Refactoring code to use Gates instead of role based check

Edit: Can not use Spatie's package right now

I know it's probably my third post relating this topic, but this time I've decided to quite redesign everything.

Right now, the way the app checks if a user can access a route is via a Role Middleware, like in the docs: https://laravel.com/docs/9.x/middleware#middleware-parameters

example usage:

Route::middleware(['role:manager,user'])->group(function () {
    Route::get('/route_x'
    Route::post('/route_x'
});

But, it makes things harder when new roles are added, because I will have to add it in many scattered places.

I decided to try to use Gates. What I want to do is to instead of authorizing based on roles, I will authorize based on the route using Gates and the can Middleware:

Route::middleware(['can:access_route_x'])->group(function () {
    Route::get('/route_x'
    Route::post('/route_x'
});

I will need to define the Gate:

Gate::define('access_route_x', function (User $user) {
    // if the user has a role that allows to view route x then return true
});

However I'm having trouble figuring how to make use of the current DB table that I already have: It's a table containing relationship between users and the role name (which is also the permission name):

user_id  | role_name
---------|------------
   11    |    manager
   65    |    user
   11    |    role_x
   65    |    role_y
   65    |    role_y
   43    |    role_z

Should I separate this table into two: relationship between role and permission, and another one for relationship between user_id and the role?

Then, if a new permission is added, I will add it to the permission table for all the roles that can use it.

Also, how do I actually write it in the gate definition? Is it something like that:

Gate::define('access_route_x', function (User $user) {
   return $user->roles()->permissions()->where('name', '=', 'access_route_x')->isNotEmpty();
});

Or I should do something else?