matrix-bot/css/organisms/RoomList.css

.mx_RoomList {
    position: relative;
    top: -30px;
    padding-top: 30px;
    padding-bottom: 10px;
    height: 100%;
    overflow-y: scroll;
}

.mx_RoomList ul {
    padding: 0px;
    margin: 0px;
}