need to attach role in registration

Dear best Team :) kindly help me how to attach role throw registration as Teacher or Student, here are my code :-

                        <label for="role_id" value="{{ __('Register as:') }}" />
                        <select name="role_id"  class="form-control">
                           
                            <option value="2">Student</option>
                             role_id = 2
                        
                            <option value="3">Teacher</option> 
                            role->id= 3
                            
                           
                        </select>
                    </div>```
Thanks in advance