do they have a crown room or comfort room at charles de gualle airport?

If you google around a bit, you will find that there are "VIP" lounges you can have access to for a price, but 7 hours is not such a long time, actually. It will dwindle to about 4 hours when you factor in the time for Passport & Immigration, the strong possibility of your plane arriving behind schedule, and the necessity to go through the lengthy security process to check in for your next flight. Another thing: Do you need to change terminals?

There are many Air France lounges at CDG. You can find them here: http://www.skyteam.com/about/why/lounges.html. Some of these have showers but all are quiet and comfortable most of the times I have been there.
You can get in these lounges if you are traveling first or business or if you are a top end frequent flyer member of any Skyteam airline such as Delta. I do not think a standard Crown Room membership on Delta will get you in, but you should check with Delta. I also do not know if you can pay for a day pass. Check with AF or Delta.
There are also other lounges but I do not know if you can buy a day pass.
You can also pay for a day pass room at the airport hotels but these are usually pricey and probably not worth it for a 7 hour layover.
There is Sheraton in Terminal 2 where you can relax in the bar or lobby.
Allow plenty of time to get to your terminal and through security at CDG. It is one of my least favorite airports.

Delta crown room clubs are now called Sky Clubs.

According to Delta's web site, if you are a member of (Crown Room) Sky Club(even flying tourist) you can access the Air France club at CDG terminal 2E On the left after Passport Control - Downstairs. They have showers.