From Nookipedia, the Animal Crossing wiki
The Roost is a café located downstairs in the museum of Animal Crossing: Wild World and Animal Crossing: City Folk, offering respite for all who wish to visit. Run by Brewster, it serves various blends (although players cannot pick the blend) of coffee for 200 Bells, one cup purchasable per day. Other special characters, such as Rover, Pelly, Kapp'n, Phyllis, and Mr. Resetti, will occasionally sit in The Roost, along with some of the player's town residents. The villagers appear in The Roost drinking a cup of coffee in Wild World and City Folk. In Animal Crossing: New Leaf, the player will be able to build this after the Museum Shop has been open for at least seven days and the Museum has at least 50 items donated.
Every Saturday night after 8pm, K.K. Slider (in Wild World and City Folk) will play music for the player. Just like in earlier Animal Crossing series titles, players can pick any song from the music list or have one randomly selected. In Wild World, players can hear another one of K.K.'s songs if there is no room in their pockets to hold a piece of music. In City Folk, K.K. will give encores, but will give players only the first song listened to, unless, as in Wild World they have no room for it. To request a song, it must be typed exactly as it is written, including spaces, periods, symbols, and capitals.
In City Folk, the coffee was given a meaningful purpose, unlike in Wild World where it was there for fun and to make friends with Brewster. If Brewster is visited every day for seven days, rather than just making friends with him, after time drinking his coffees will eventually lead him to ask the player if he or she would like to store gyroids with him. This frees up lots of space in the players house's closet and rooms. He keeps only one of each gyroid though. However, to achieve this, the coffee must be drunk right away while it is still piping hot. It is possible to see a few gyroids on Brewster's shelves. This is easiest to do during a K.K. Slider show.
Animal Crossing: The Movie
In Animal Crossing: The Movie, Ai comes to The Roost in order to find Apollo. Once she arrives, she meets Cesar and Cyrano. Once Apollo arrives, she delivers the package that he had ordered from Tom Nook, then apologizes for the destruction of his flowers, which she had accidentally crushed during the delivery. Apollo compliments Brewster on his coffee, takes his package, and leaves.
Animal Crossing: New Leaf
The Roost reappears in Animal Crossing: New Leaf as a public works project, obtained from Blathers seven days after renovating the Museum to include its shop. In addition to enjoying coffee served by Brewster, if the player buys coffee at least seven times, they can have more options for their coffee (i.e. adding milk, sugar, and selecting the type of beans used) and will be able to hold a part time job. You will serve at least 3 villagers/special characters/people not from this town when you start your part time job. You can also talk to villagers sitting at the counter, and occasionally, you will see a special character sitting at the counter. Three gyroids can be seen at The Roost. An Oombloid is in the pot in the front, and a Tall Gongoid and Mega Buzzoid are on the shelf behind Brewster. If the player wants they can take coffee outside, to drink it press the A Button.