Writing new user plus roles to the database.

I have a simple form for creating a new user which includes a checkbox list of all the available roles. I'm trying to figure out how to iterate through the roles once the user has been created and then save the roles to my roles table.

public function store(Request $request)
{
    $rules = array(
        'name'      =>  'required',
        'email'     =>  'required|email|unique:users',
        'password'  =>  'required|min:10'
    );

    $validator = Validator::make(Input::all(), $rules);

    if($validator->fails())
    {
        return Redirect::to('admin/users/create')
            ->withInput();
    }else{
        $user = new User;
        $user->name = Input::get('name');
        $user->email = Input::get('email');
        $user->password = Hash::make(Input::get('password');
        $user->save();

        // How to get the roles
        // Then iterate over them to save them to my user_roles table.

        Session::flash('success', 'Your new user has been added.');
        return Redirect::to('admin/users');
    }
}

Checkboxes look like

@foreach($roles as $role)
    <div class="checkbox">
        <label>
            <input type="checkbox" name="roles" id="role_{{ $role->name }}" value="{{ $role->id }}" /> {{ $role->display_name }}
        </label>
    </div>
@endforeach