A roster bonus is another form of compensation for NFL players. If a player contract contains a roster bonus in it, it is considered earned when the player remains on his team’s roster on a specified date. This type of bonus typically counts against the salary cap, in whole, during the League Year that it is earned.
There is an exception to this. If a roster bonus is guaranteed for skill, cap and injury at the time of signing. These types of roster bonuses are treated like a signing bonus and can be prorated over the life of the deal (with the five-year max).
Teams, who would rather not push large amounts of money into future caps, have begun to use the roster bonus to skirt proration. By not guaranteeing a roster bonus until, say, a week after the deal is signed, the team can take the entire charge of the bonus in the season it is due and avoid any dead money from it in future years.
Another form of this is the per-game roster bonus. These bonuses “reward” a player for being on his team’s 46- or 53-man roster in a given week. Depending on the stipulation, a player will earn this money if he is on either the team’s active (46-man) or inactive (53-man) roster. This puts the pressure on the player to stay healthy because of the financial ramifications an injury can have. These bonuses are not favorable for the player unless added on top of an already strong contract.
Example: JJ Watt and Colin Kaepernick
When JJ Watt and the Houston Texans agreed to a six-year $100-million deal in 2014, the contract had a $10-M roster bonus, due in 2015, that become fully guaranteed one week after Watt signed on October 3. By doing this, the team avoided prorating more money into the future but still committed to paying Watt that money.