The Response for Landroval says that a hero once destroyed can be put back into play, but that there is a limit of once per game. If the Landroval card leaves play at some point after this response has been triggered, and then enters play again either via the play of another Landroval card or retrieval of the Landroval card from the discard pile can the response be triggered again?

In fact, Landroval leaves play immediately upon using his ability (he goes back to your hand as part of the cost). In order for the restriction to make any sense whatsoever, it's gotta be that Landroval's ability can only be triggered once per game, period. (There's no way for the game to "know" whether the Landroval you've played is the same one you played before or not.)