The Roost is a coffee shop in the island museum where you can hang out with villagers and friends while sipping a cup of coffee. It is a feature in Animal Crossing: New Horizons added during the 2.0 update.
The café is not readily available when you update the game. First, you need to have the museum upgraded and then unlock the art gallery.
After this, Blathers will tell you he wanted to draw more people to visit the museum, and so he thought of adding a café. He will ask you to look for his friend, Brewster, an expert café manager, and give you a photo of his friend for reference.
Where to Find Brewster
In your last conversation with Blathers, he mentioned someone named Kapp’n and that he could take you on a boat tour to a random island.
The first time you go on a tour with Kapp’n, the island you arrive at is where you will find Brewster. Talk to him and tell him about Blathers’ idea, and he will accept.
The next day, Isabelle will announce that the island’s museum will be closed for the day because it will undergo a renovation to add a café.
Welcome to the Roost
When the museum is open again, Blathers will thank you for finding Brewster. The café is located up the stairs to the right.
Inside you will find Brewster as the barista.
You can get a cup of coffee for 200 Bells. Just sit on the counter, and Brewster will brew you a hot cup.