Putting chickens together can be tricky:/ .NEVER EVER put chickens together during the day time, major fights will occur. The best thing to do, is to put the together at night, after its been dark for a couple hours. If you do this super quiet, the other chickens won't even know they're there...
As for getting a rolling coop, depending on where you get it from, it mostly likely will fall apart. The ones you build are much better then the ones that you buy! Your best bet is just securing the top of the run you have already!
Good Luck!