I recently got 5 broken Roomba robot, with the purpose of scavenging useful parts and trying to assemble one frankenstain style.
Motors are working!
The motor assembly is always working, is the sturdiest and more reliable part of the robot.
The motor has an encoder, which is analised on the motherboard, an endstop switch which connects when wheels are pressed against the ground and a spring that compress between 800 and 1200g.
The motor assembly weights ~250g.
Motors are powered at 12v dc.