Maybe

def can_list_bots?(team_id, user_id) do
  team = Repo.get(Team, team_id)
  user = team && Repo.get_by(User, id: user_id, team_id: team_id)

  if user do
    "admin" in user.roles
  else
    false
  end
end

or if you want with

def can_list_bots?(team_id, user_id) do
  with team when not is_nil(team) <- Repo.get(Team, team_id),
       user when not is_nil(user) <- Repo.get_by(User, id: user_id, team_id: team_id) do
    "admin" in user.roles
  else
    _ -> false
  end
end

or with with pattern matches

def can_list_bots?(team_id, user_id) do
  with %Team{} <- Repo.get(Team, team_id),
       %User{roles: roles} <- Repo.get_by(User, id: user_id, team_id: team_id) do
    "admin" in roles
  else
    _ -> false
  end
end

You can also do it in a single sql query. Probably.