Laravel error while trying to migrate

I want to add another column to my database table users. I made a new migration named "Modify_users_table" which has the code to add the column. There is nothing wrong with the code because I used it before, but it gives me an error that something is wrong with the table roles? How can I solve this? Here is the error and the code that is related to the error

Here is the migration "Roles"

 public function up()
{
    Schema::create('roles', function (Blueprint $table) {
        $table->string('role_name')->length(55)->unique();
        $table->increments('id');
        $table->timestamps();
    });
}

via Chebli Mohamed