What kind of robot are you attempting to loot? In Fallout 2 there are restrictions on what kind of corpse you can loot, so you can't loot the large standing robots or the small security drones (Floating eyebots), but you can loot the short, squat robots with the dome head and the long arms. They carry and use regular weapons (Mostly mundane weapons, a few might have sniper rifles), and all in the depot will have a motivator on them, too.
If you really want to loot the big robots, you can kill them on a hex where something else died (Or, alternately, kill something on the hex the robot died on) and loot that corpse, then use the arrows on the loot interface for multiple corpses to cycle over to the robot, I think they might carry either rockets or a chain gun, not sure. You usually get a few like this if you take on the Enclave by force since you end up with bodies littering the halls like cordwood.