It is fine to let him run around your room as long as you make it piggy proof. Make sure there are no wires he can chew or little gaps he can squeeze into. Guinea pigs should have floor time everyday as they need exercise.
I found that he loves my walk in closet. Its easy for me to catch him and there is nothing he can get into : ) Of course he is strictly supervised. I just hope he does not pee on the floor {:|
More improvements to his cage are coming today!