I'm a vertically challenged senior citizen. I've covered my prior 23' and now my 32' travel trailer by myself. If you can climb a ladder carrying 30 lbs or so you should be able to do it. It's a lot easier to do if you have a roof you can walk on and if you have a place on the ground large enough to lay the cover down and roll it up in a way so that it's in the correction orientation when you roll it out on the roof. Be careful and don't do it on a day with any wind.
As for just the roof or the whole trailer, the hardest part is getting it up on the roof. Once you roll it out draping it down the sides is the easy part.