xD and he answered. Concobar, not every crews main members have to play those roles. Usually, small crews like Straw-Hat pirates have to have assigned roles, and I think the same would be for Blackbeard pirates, but before timeskip, when there were not more than about 10. However, now when Blackbeard officially has Yonko status, they surely recruited vast numbers of pirates into their crew who would do those assignments for them. Besides, I cant imagine being a Yonko with only 10 people.