so a minimum of 3 & max of 6 prospects can be on your roster?
No, let me clarify — There are no rules for prospects. You can draft a team completely devoid of them if you'd like.
However, I strongly discourage any team from having too few or too many at season's end. This is a dynasty league, so they're valuable. But I don't want anyone strictly playing the long game and punting contention for this season.