WARNING: Spoilers for Palm Springs.
What happens in the post-credits scene for Hulu's Palm Springs ties up one loose end from the film. Hulu's new romantic comedy starring Andy Samberg (Nyles) and Cristin Milioti (Sarah) is now streaming after a record-setting Sundance deal. Palm Springs revolves around Nyles and Sarah's individual and combined experiences in a time loop that is set around Sarah's sister's wedding. By the end of the movie, they've managed to break the time loop and return to a normal life.
However, Sarah and Nyles are not the only people stuck in the time loop. Nyles is the first one to enter the loop and does so before Palm Springs even begins, and he managed to bring someone else into the loop before Sarah. During one of Nyles' many days in the loop, he meets Roy (JK Simmons) at the wedding reception. The two have a wild night together and Roy mentions that he wishes this could do this forever, so Nyles takes him to the cave that causes the time loop. Once Roy enters it, he becomes stuck in the loop, making it impossible for him to watch his family grow up. Roy begins to torture and kills Nyles repeatedly to get his revenge before figuring out that it wasn't worth it.
By the time Palm Springs ends, Nyles and Sarah might be out of the time loop, but Roy's fate is left unresolved — until the after-credits scene. The scene shows Roy returning to the wedding and he finds Nyles to tell him about the message Sarah left. This message to Roy lays out Sarah's method for breaking the loop and Roy is filled with joy at the prospect of it being true. He quickly figures out that this is possible since Nyles does not recognize Roy anymore. Roy then offers to buy Nyles a drink and the scene ends before it is shown what happens to Roy after.
This might leave viewers with a question about whether or not Roy does manage to break the loop, but it is heavily implied that this is in his future. If Sarah left him a message before she and Nyles broke the loop, then Roy should have correct instructions on how to do it himself. All he has to do is strap a bomb to his chest and enter the cave again but detonate the explosion during the 3.2-second window when the box of energy that created the loop is taking him back to the beginning of the day.
As long as he follows Sarah's direction, there's no reason to believe that Roy wouldn't break the loop too, especially after he sees that Nyles already did it. On the off-hand chance that Roy can't figure out what Sarah told him to do, then he would just continue to live out the same day over and over. Maybe that will leave room for a Palm Springs sequel/spinoff that focuses on Roy's attempt to break the loop. But, that could be avoided as long as Sarah's instructions were made clear to Roy.