I already own Titanfall 2 on disc and it is free this month on PS Plus. The PlayStation is still telling me to insert the disc when I try to play it. Is there a way I can play the game without needing the disc any more since its a plus game now?
The digital version and disc version are the same game but different in how they work. You need to delete Titanfall 2 from your PlayStation 4 and then go to the store and download the digital version. Once this version is installed you will not need to use the game disc you own in order to launch the game.
Keep in mind, if your plus subscription ever ends, you will need to go back to using the disc based version of the game.