I use a stamina/durability combo approach to determine if a guy can do LRA or LRB. From purely stamina, 50-65 works for me, but if a guy is effective, has a stamina of 43 but a durability of 70+ (meaning he can bounce back fast) he could fill that role. I do this for all roles, some guys become starters with a stamina of 60 because of a durability of 30+.
I have had a stamina 32 guy fill SUA with a durability of 80+. Starters get the most innings, so if a guy is effective, and can fill the role, you want him there. Next would be SuA for me, they tend to eat more innings for me than a LRA guy. Closers are optional, some of my teams I don't use closers. My sweet spot is to look for a stud SuA that can eat up 170+ innings in a season, a guy with good ratings across the board with a stamina/durability of about 40/90 can be key.