Discounts for different user groups (roles)?

Question

Laravel

hello everyone, I make discounts for different user groups (wholesaler, etc.). Here is the database architecture.
The essence of my implementation:
in a separate section of the admin panel, you can create, edit, delete, and make a discount available / not available. Inside the discount, I chain products
id
product_id
role_id
title
sale_price
date_start
date_end
Here is the ProductSale model

public function products()
    {
        return $this->hasMany(Product::class);
    }
  
  public function roles()
  {
    return $this->hasMany(Role::class);
  }

the form

<div class="form-group">
    <label for="">Customer Group</label>
  <select name="roles_id[]" class="form-control select2" multiple>
    @foreach($roles as $role)
      <option value="{{$role->id}}"
      @isset($sale->id)
        @if($role->id == $sale->user_role_id)
          selected
        @endif
      @endisset
      >{{ $role->title }}</option>
    @endforeach
   </select>
</div>

<div class="form-group">
    <label for="products">Products</label>
  <select name="products_id[]" id="products" class="form-control select2" multiple>
  
    @foreach($products as $key=>$product)
      <option value="{{$key}}"
      @isset($sale->id)
        @if($key == $sale->product_id)
          selected
        @endif
      @endisset
      >{{ $product }}</option>
    @endforeach
   </select>
</div>

I can’t make an insert in any way, or I made a mistake in the database architecture, tell me?