You didn't say what kind of rv you have, and what you want to achieve, so no answers can be given... Because you are posting in Class A forum so I assume you have a class A DP and you want to have a decent solar system on it... Here you go - I would suggest to put up 2 x 145w up there, this way you don't need to redo it down the road. Make sure use thick wires (6 or 8 gauge) with a 40A (minimum 20A) MPPT controller. This setup will provide sufficient power for your boondocking in most conditions.
Steven & Polly
2000 Country Coach Intrigue 40' ISC 350
2014 Ford C-Max Energi