All of Roach's characters were a clone of the same man. Rewatch the trilogy with this in mind, and suddenly a whole awesome yet unspoken subplot appears.
In Raiders, it's mentioned that Hitler has become obsessed with the occult (it's why he wants the Ark of the Covenant, other than the fact that he really needs an accent table for his new office). Now, the Thuggee seem well-versed in black magic, considering they had no trouble turning Indy into their own voodoo doll.
Which probably worked a little too well.
So what if Hitler heard about this group and went all Hellboy, using both Nazi science and black magic to extract the Thuggee guard's DNA to perform some occult cloning experiments (remember that although it's the second film in the series, Temple Of Doom takes place before Raiders). This would explain why the Nazis employ multiple henchmen who look like Roach. He was their first successful test subject in their attempt to create a terrifying killing machine ... who is also genetically predisposed to always get his ass kicked by an archaeology professor.