Carry on question

You should check the airline's requirements. I usually fly Delta and I take one 20" rolling carryon and one personal item. Some budget airlines may be more strict about how much you bring into the cabin.

You should be OK but the emphasis is on "should." Check with the airline, as recommended. Most US airlines allow two bags. One in the overhead bin and one under the seat. However, it will depend a bit on the size of the backpack, how full the plane is, and the attitude of the gate personal. And a regulation size bag may not be regulation. Often a carry on bag is advertized as carry on but the handle and wheels do not fit into the sizing box so it really is not carry on. Do you know for a fact that your rolling bag will fit inside the sizing box?

Delta is 22" by 14" by 9", so you should be OK, but measure it with the wheels and handle.
Hint: Gate personel have an eagle eye out for roller boards, but a blind spot for backpacks IF you are wearing them. Its your "personal item", which you can also bring. Besides, its against the rules for a computer to be in checked luggage.

Major airlines flying Intercontinental from the US always seem to allow a carry-on bag and a personal item. The carry-on bag would be your roller – make sure that it fits into your airlines rules. The backpack will be your personal item that will go under the seat. If you're flying one of the major airlines you should be fine with us. If it's a smaller or very low budget airline I would doublecheck it.

But you may very well be asked to "gate check" your roller bag. This means you will roll it through security and onto the plane with you but when you try to get on, the gate agent will take it, tag it, and give it back to you when you get off the plane. You will not have to go to baggage claim - it will be waiting when you get off. This happens when the plane is very full. Best to make sure anything urgent is in your backpack if this happens. That would be a passport, medication, that kind of thing just in case. And of course anything you need on the plane like books magazines etc.

As said, check the carrier for their specific carry-on (and checked baggage) rules. That said, be aware that the operator may be a partner or code share airline. For example, book on Delta but you may be on a KLM or Air France operated flight. KLM and AF have cabin baggage weight limits while Delta doesn't have a weight restriction.

Delta warns:

AIRLINE PARTNER NOTICE Our SkyTeam® and codeshare partners may have
different guidelines and restrictions on certain flights, so be sure
to check before you check in.

I'm curious about the "gate-checking". I have only done it on a domestic flight, but in those instances I always have to retrieve it in baggage claim. Is it different internationally?

Generally, when you "gate check" you tag your bag and turn it over as you are getting ready to board your plane. So it is after security and the "normal" checked baggage procedures. So far, I have never had to go to baggage pickup to get it..... always right near the plane itself.

.... So far, I have never had to go to baggage pickup to get it..... always right near the plane itself.

Depends. Short hop regionals like Horizon and Skywest allow carry-on bags to be ramp s pool checked and retrieved. For others:
http://www.businessinsider.com/dont-gate-check-your-bag-2013-10

But fear not, United then told us, because the gate agent would be
happy to check our bag right there. We could pick them up at baggage
claim back in New York.....the kind of gate-checking that requires you
to wait to pick up your bag at baggage claim, not plane side.

Can you image the congestion at the exit door if passengers had to wait for gate checked bags to be unloaded planeside and brought up to the skybridge?

I will be on USAir for the flight to London in business class and the return is economy. It is a nonstop flight both ways. My backpack is not one with a frame its foam sided and less than half the size of my roller. Just big enough for 2 camera's and a Surface tablet. I was considering leaving one camera and putting my CPAP in the backpack. I hope the CPAP is not a problem in security checks.

No guarantees, but with a Business Class ticket, I think you'll be fine. I have no idea what a CPAP is, so can't advise on that. If you are asked to gate check, just (and only then) explain why you are carrying on the cameras...that you were concerned re: checking them. Flight attendant may find a special plane on the plane for them, if overhead is full.

But, again in Business Class, there is usually ample overhead.

Now, on the way home, when you are in economy, you might be prepared to gate-check your rollaboard, if needed (so put anything really valuable in with the cameras.)

I've been "told" to gate check a number of times, generally with short hops in which my bag "technically" is within carry on requirements but will not fit overhead on the tiny plane they are actually using that day. I was never offered the option to have my bag checked through to the final destination, although apparently that does happen at times. In the past I have picked up my bag either immediately after deplaning (all the bags come on a cart) or when standing by the exit door of the plane (yes, a bunch of passengers standing around waiting for their luggage like a mini luggage claim.) As I said, it has always been a last minute issue with me. However, I have heard various airline ticket people just prior to boarding, offer to check bags for people that would be sent to their final location. I asked one about it and she said the flight was full and they hoped to create more overhead space by offering to do that for people. A different situation than being told passengers must gate check because of plane size.

From what others have reported, CPAP machine is approved carry on as medical device (does not count against your carry on allowance).

What Laura B just said is correct. A CPAP is a medical device and does not count in the carry on formula. Having said that, my husband "discovered" on our last trip that he could get by with only it in its case. He put his meds, his European extension cord and his iPad in there with plenty of room. He carried it on with his RS convertible backpack and that was the extent of his luggage.

Depending on the airport we leave from, he may or may not have to open up the case, take out all the parts and put them all in a bin. Atlanta seemed to be very picky about that. However, once we magically (we did nothing to deserve this) got TSA Pre-Check status, he has never had to do that again. He's also never had to do it going through security within Europe or on the way home.

He carries no camera gear and only rarely takes a picture with his smart phone. I do all the picture-taking, now only with my smart phone. Needless to say we are not photographers. We simply take pictures to have a memories of our trips, and I discard about 80% of what I take either on the fly or after we get home. So that avoids the need for a special camera bag.

I have had to gate-check a couple of times, retrieved the bag near the plane exit door unless there were stairs instead of the jetway. No congestion issues, but I've always had to wait a few minutes for the bag, so if you have a tight connection you may want to check it through to your destination rather than gate-check it.

You won't have a problem on the business class leg. The return trip may be more debatable, but checking a bag on the way home is no problem. If you are in zone 1, 2 or 3, you probably won't have to check a bag, but zones 4 and 5 often do (at least on domestic flights). The CPAP should be in a separate bag (you could put your meds in that bag, too), and does not count as part of your 'limit' - do NOT check it under any circumstances.

I'm assuming you are flying from Charlotte. You can use any of the TSA lines as you can access all the gates once you leave the TSA area. The A and D TSA lines are sometimes shorter as people go to B and C because they are closer to the check in desks. If you have time before your trip, consider getting the Global Entry (cost is a one time fee of $100) which includes TSA pre-check and saves you time at immigration check when you return home as you can self check in!!! You can do the required interview at the Charlotte airport.