app/views/projects/_role.html.erb
<div style="text-align:center">
<%= form_tag grant_role_project_path(@project), remote: true, data: { update: "#role_list"}, class: 'form-inline remote-form' do -%>
<label for="role_user">Select a user</label> <%= select "role", "user", @users.map {|r| [r.name, r.id]}, { prompt: true } %>
<label for="role_authorizable_type">then assign a role</label> <%= select "role", "authorizable_type", @all_roles, { prompt: true, } %>
<%= submit_tag "Add role" %>
<% end -%>
</div>