Sorry about that. Hope you understand what I'm saying.
If your rooster shows evidence of double barring then 100% of the offspring, males, & females will be Barred.
If the rooster shows evidence of being single Barred, then about 12% of the offspring will be Barred, & solid colored.
The chick you posted is a cockerel.
If the Buff Brahma was 100% the mother, the color of the chick should resemble something like this.
Since the chick you have is a male, that means the Barred Rock is the mother of the chick.
This is a project Orpington of mine I'm using for example.
Could be possible. I thought maybe you did.
Here's some comb genetics for you.
Rose comb = R/R, R/r
Pea comb = P/P, P/p
Single comb = r/r, p/p (Recessive)
Walnut comb = R/R P/P _ R/r P/p _ R/R P/p _ R/R (Four different combinations)
It's very possible.
I hatched a blue Cuckoo colored chick recently from a Blue Wheaten, crowing bantam rooster, crossed with a dominate white silkie. So one of the parents must carry the barring mutation somewhere in their genetics to produce Barred offspring.
The Barred Rock hen is most likely the mother.
All barred chicks will be male if a solid colored Male mates with a Barred female.
Female chicks won't be Barred.