There is no way to get the exact role of the user that you have assigned in your GAE dashboard, but you can check if the currently logged in user is on that list. If you are using Python here is how you can achieve that:
from google.appengine.api import users
user = users.get_current_user()
if user:
print 'Welcome, %s!' % user.nickname()
if users.is_current_user_admin():
print '<a href="/admin/">Go to admin area</a>'