New Answer:
Notice that the puzzle’s wording is

“If I used to be to inform you the next: … Then who’s a rock and who’s a roll?”

Therefore,

for the reason that puzzle is unimaginable, you are a rock!

Old Answer, not appropriate due to data I discovered via feedback beneath:
I feel

all three need to be rocks

Here are the attainable outcomes for the 6 potentialities:

A is a roll –> Rock, Rock, Roll
A is a rock –> Roll, Roll, Rock OR Rock, Rock, Rock
B is a roll –> ?, Roll, ?
B is a rock –> ?, Rock, ?
C is a roll –> Rock, Rock, Roll OR Roll, Rock, Roll
C is a rock –> Rock, Roll, Rock OR Roll, Roll, Rock

If A is a roll, the one attainable consequence is that A is a rock. That contradiction means A can’t be a roll, which suggests A should be a rock, which suggests all are rocks.

So we’ve the reply already, however simply to be thorough, let us take a look at whether or not can B be a roll. Since B claims to be a Roll, this contradicts A being a rock, which we already know, so B should even be a rock.

Lastly, can C be a roll? No, as a result of they declare that each they’re a roll (false) AND that B is a rock (true). C being a roll would contradict A. Also observe {that a} FALSE AND’ed with a TRUE is fake, that means that C should even be a rock.