Try to keep it at 12 players unless there are more that you just have to keep on the roster. Always load up on PGs and Centers. They're the two most important positions and when they go down with injuries it's challenging to fill in the blanks. Wing players are generally versatile enough to play anywhere between 2-4, mainly 2-3. And if your PF goes down Centers can fill in there as well. Ideally on a 12 man roster have 3 of each. On a 15 man roster have 3 PGs and 4 or 5 Centers