the size depends on the type of uro. Egyptian uros are the biggest and can get pretty large, close to the size of an adult dragon. Mine is a saharan uro and Im pretty sure he is full grown at about.... (going to check right now.....) he is about a foot give or take an inch or two. I don't have a measuring instrument at the moment but might be able to get measurements later tonight.
As for them being housed together. That is out for debate and since I only have one uro, I have no experience with that, and therefore, no room to get information about. I have seen people saying they are solitary animals, but I've also seen them housed together. It could all just depends on the temperaments of the two uros.
-Brandon