colosseum, underground and third ring and Roma Pass

If I have the Roma Pass, can I just call them to book the tour or do I
have to buy the ticket on-line?

You can do it either way. If you do it online, all you'll be doing is booking the tour: show your Roma Passes at the reservation desk when you arrive for your booked tour slot. If you do it by phone, tell them you'll be using the Roma Pass so don't need separate entry tickets. Again, show you passes when you arrive.

If I can book by phone, how early can I call them? Is it the same as
booking the tour on-line, i.e. third Monday of the month before the
following month?

Whether by phone or online, bookings open at 9:00 AM Rome time on the third Monday of the month for the following month. They can sell out within minutes so you must be online or on the phone at whatever 9:00 Rome time is in your part of the country.

http://www.coopculture.it/en/ticket.cfm?office=Colosseo%2C%20Sotterranei%20e%20Terzo%20Ordine&id=0&evento=6

Please let me know if this is the correct process to follow:
I want to purchase 2 entrance tickets and 2 underground tour tickets for mid October.

1. On September 18th at 9 AM Rome time log on to the coopculture website
2. buy 2 entrance tickets
3. buy 2 underground tour tickets

Do I purchase them in this order or can I purchase the underground ticket first since it is of limited quantity.

Robbie, I wouldn't even bother with entry tickets. Buy your tour tickets online and purchase your general entry tickets at the reservation desk when you arrive for it as you have to go there anyway. The only reason I'd purchase them in advance is if you want to visit the Forum/Palatine BEFORE you go to the Colosseum: you would have to have your general entry tickets in hand to do that. That said, yes, you can purchase your tour and entry tickets at the same time but do tour tickets FIRST as when those are gone, they're gone, and they go so quickly.

Another option if wishing to do the Forum/Palatine first? Ticket lines are shorter at either (shortest at Palatine) so if willing to stand in a queue of undetermined length, you could purchase your general entry tickets there before your tour of the Colosseum. A ticket allows you a single entry to the Forum/Palatine (must be visited together) AND the Colosseum, are good for two consecutive days: can visit the Colosseum on one day and the Forum/Palatine on the next - or vice versa - if wishing to split your visits.

Just got a reply from coopculture.it and confirmed that the underground tour must be booked on-line.

The underground tour should be booked online. Only the regular tour is booked by phone. You don't need to purchase your entry tickets at the same time as you purchase the underground tickets, in fact, trying to book both slows down the process. You can book entry tickets at any time as they are not time nor date specific.

Donna

The underground tour should be booked online. Only the regular tour is
booked by phone.

Just to clarify, Donna, as far as I know - and Rick's 2017 Rome guide states as well - they can be booked over the phone as well as online. The coopculture site appears to provide that option in the "Buy through the call center" text, which doesn't indicate that the phone option doesn't apply to these tours. True?

I ran across Rick's advice here:

https://tinyurl.com/y76ucj9c

"A longer, 1.5-hour tour takes you through areas that are off-limits to regular visitors, including the top floor and underground passages....advance reservations are strongly advised, either by phone or online (no same-day reservations). Use the same website as for regular tickets (www.coopculture.it) or contact the call center (see "information" earlier). After dialing, wait for English instructions to reach a live operator."

Worth the clarity as, given how rapidly these ticket are sold out and reported length on time people have had to stay online to get them, they might try BOTH methods simultaneously to see which gets them through most quickly.