public function show($employee)
 {
     $employee = Employees::find($employee);
     $roles = Roles::pluck('role_name', 'id');
 return view('employees.show')->withEmployee($employee)->withRoles($roles);
}

<div class="form-group">
<label class="col-md-4 control-label" for="roles_id">Role</label>
<div class="col-md-4">
<select id="roles_id" name="roles_id" class="form-control">
<option value="{{ $employee->roles->id }}">{{ $employee->roles->role_name }}</option>
</select>
</div>
</div>