>>34114256>>34114297>>34114383>>341144201. If it looks sad, it is an implication to talk to it, tap the sides to interact with it.
2. You can unlock features by befriending rotom by getting rotto-items (basically o powers) but its a chance, only when his eyes glows.
3. He also (randomly) allows you to use a z-move again.
4. He gives you a nickname based off the first letter of your ingame name- with the prefix being 'Rotto'.
5. Eventually he will ask if you want to be called master.
This shit is honestly NOT hard to figure out. Lol.