No matter what size the enclosure is they should breed just fine, as long as they are not super overcrowded. To get high numbers of nymphs just make sure all their conditions are satisfied : food, water,heat,ventilation,humidity. Other than that they just need to be left alone to fo what roaches do. Breed!!! Like roaches.
The standard would be a medium sized plastic tub. I would not get too large of an enclosure because of convienance issues like space and heating requirements.