A "roster spot" refers to a position on a sports team. It means being officially chosen and included in the group of players who are eligible to participate in games or matches. Full definition
In terms of roster spots that shouldn't really be too much of an issue. (sbnation.com)
Right now he is just a wasted roster spot. (sbnation.com)
That he has to give roster spots and ridiculous contracts to veterans because if you play the kids you lose, and nobody wants to see a losing team. (sbnation.com)