If (player is in a room) {
  Use earth spell
}

Or something like that.
Will something like...

if (player.parent = room) {
  Spellcode
}

Work?

Should do.

if (game.pov.parent = room) {

is the standard way to do it, but in some circumstances it might be better to use

if (Contains (room, game.pov)) {

Looks good. Thank you!