adding a specific roles to user to see something on the page

although i had this question before but did not get anything useful and am stuck. Ok my app is a simple ebay clone, where i had divided users into roles buyers and sellers with role id 1 and 2. When anyone sign up or login they are transferred to the index page of the app, Now i want buyers to see something different then sellers on the index page and for that I had tried the if and else method but nothing happened. Is am doing anything wrong? I there any other way to get on this.

My Index.html.erb file

    <div class="col-md-12 text-right">
        <% if role_id == 1 %>
            <%= link_to "Add a new Product", new_product_path, class: "btn btn-success" %>
    </div>
    <% else %>
      <div class="col-md-8">
        <% @products.each do |productt| %>
    <div class="product">
    <h4><strong><font style="text-transform: capitalize;"><%= shipment.user.full_name%></strong></h4></font>
    <h5><strong>DESCRIPTION: </strong><%= product.description %></h5>
     <div class="thumbnail">
    <td><%= image_tag product.image.url(:medium)%></td>
      <div class="meta">
        <%= link_to time_ago_in_words(product.created_at) + " ago" %>
        <span class="admin"> 
          | <%= link_to "Show Details", product %>
       </span>
     </div>
    </div>
   </div>
  </div>
 <% end %>
<% end %>

and

My seeds.rb

['buyers', 'sellers'].each do |role|
    Role.where(name: role).first_or_create
end