Roller if you’re fancy, smaller operations just use a ring cutter. (Source, me, I was baker and hand-cut a couple thousand circles most nights) We didn’t actually fry the holes though, more for process efficiency than anything. They got re-formed into a slightly firmer dough for cinnamon rolls and fritters. “Donut holes” were cut with a small roller with a hexagon pattern.

Cake donuts are indeed different because they’re made from a liquid batter. Fancy hopper on an arm over the fryer, drops perfect rings of batter into the oil when you turn a crank.