Yes, I think so. Because they show behavior that is consistent with being in a state of pain.
Despite what consciousness really is, I think evolution found a way to tap into that, by causing pain, or by registering pain on the consciousness by some unknown mechanism, for behaviors that are not beneficial to the organism that hosts the respective consciousness...
So I think if an organism that evolved here can display painful behavior, then it should really feel pain.
So to match with that your hypothetical scenario should involved robots that already have consciousness within them and the question would be if their evolution had managed to tap into that built in consciousness and ability to feel and cause them to behave in one way or another.
They're not reducible, but I don't know if that means we don't have definitions; we can describe them well enough that most people (who aren't p-zombies or playing the sceptical philosopher role) know pretty well what we mean. All of our definitions have to bottom out somewhere...
> Do insects feel pain?
Nobody (except the insects) can know for sure. Our inability to know whether X is true doesn't imply X is meaningless, though.
In the comment that started this subthread, qsera was responding to someone who said "Imo we don't even have a definition of [consciousness]". If qsera meant that we can measure consciousness in terms of pleasure and pain, then of course I agree that they were just pushing the problem back a step. But I don't think that's what they meant.