The NFHS has released their 2012-13 Soccer Rules Interpretations ....

SITUATION 1: A player who is not listed on the roster scores a goal. The goal is allowed. RULING: Legal.
Since players may be added to the roster after the start of play, a goal by a player who is not on the roster should be allowed and the player’s name and number should be added to the roster.  (3.1.3 Situation A)

SITUATION 2: Goalkeeper A fouls Opponent B in the penalty area resulting in a penalty kick for Team B. Goalkeeper A is disqualified for committing serious foul play. Team A is permitted to substitute a goalkeeper from the bench but must have a field player leave the field. RULING: Team A must play short due to the disqualification (12-8-2, 12-8-4), but must have a goalkeeper (3-1-1).  (3.3.2 SITUATION B)

Read more.