Youtube has it online in 7 parts. Part 1:
part 2, part 3, part 4, part 5, part 6, part 7
Moria opens their review with this:
Robot Monster is one of the classic so-bad-its-funny turkeys from the 1950s. It’s right up there in terms of ineptitude along with Plan 9 from Outer Space (1959)
Robot Monster is a film that is hard to hate – it gets a four star rating here because the cheesiness of its ineptitude provides such an enormous degree of sheer entertainment value.
1000 Misspent Hours says it
stands among (and in my estimation, even exceeds) such films as Plan 9 from Outer Space and The Giant Claw as a true archetype of deliriously lousy 50’s science fiction.