Yes, you can eager load only specific columns from relationships. From the docs:
You may not always need every column from the relationships you are
retrieving. For this reason, Eloquent allows you to specify which
columns of the relationship you would like to retrieve:
$books = App\Book::with('author:id,name')->get();
When using this feature, you should always include the id column and
any relevant foreign key columns in the list of columns you wish to
retrieve.
In your case it would be something like this:
UserModel::select('userid', 'locationid', 'username', 'firstname', 'lastname')
->with('subRoleName:id,column2,column3')
->get();
But as the documentation says be careful to always include the id and the relevant foreign keys, otherwise it won't be able to load the relationship properly.