I use pellets because in each bite they get a bit of everything but with crumbles and mash they may pick through it and don’t get enough nutrients. Pellets are more compact and crumbles and mash are pretty much just mashed pellets. Crumbles aren’t mashed as much as mash.
Roos can have layer feed but it is not best for them they need more protein than calcium which is in hens food. I currently feed my hens Purina Layena. Purina flock Raiser Feed, contains 20% protein and around 1% calcium, making this an excellent rooster food source. But not so good for laying...