Código limpo para ler

codigo.py

# sem linhas em branco, código não tão junto
if current_user.has_role('admin')
    cases = cases.of_product(product)
elif current_user.has_role('employee')
    cases = cases.of_product_accessible_by_employee(product, current_user)
elif current_user.has_role('customer')
    cases = cases.of_product_accessible_by_customer(product, current_user)

codigo.rb

# sem linhas em branco, tudo muito junto
if current_user.role? :admin
  @cases = @cases.of_product @product
elsif current_user.role? :employee
  @cases = @cases.of_product_accessible_by_employee @product, current_user
elsif current_user.role? :customer
  @cases = @cases.of_product_accessible_by_customer @product, current_user
end


# com linhas em branco, muitas linhas
if current_user.role? :admin
  @cases = @cases.of_product @product

elsif current_user.role? :employee
  @cases = @cases.of_product_accessible_by_employee @product, current_user

elsif current_user.role? :customer
  @cases = @cases.of_product_accessible_by_customer @product, current_user

end

@lucasdavila eu faria exatamente como tu fez, a única diferença seria os parenteses, que geralmente eu coloco

if current_user.role?(:admin)
  @cases = @cases.of_product(@product)
elsif current_user.role?(:employee)
  @cases = @cases.of_product_accessible_by_employee(@product, current_user)
elsif current_user.role?(:customer)
  @cases = @cases.of_product_accessible_by_customer(@product, current_user)
end

outra solução é partir para o case

case current_user.role
when :admin
  @cases = @cases.of_product(@product)
when :employee
  @cases = @cases.of_product_accessible_by_employee(@product, current_user)
when :customer
  @cases = @cases.of_product_accessible_by_customer(@product, current_user)
end

ou

@cases = case current_user.role
when :admin
  @cases.of_product(@product)
when :employee
  @cases.of_product_accessible_by_employee(@product, current_user)
when :customer
  @cases.of_product_accessible_by_customer(@product, current_user)
end

que nesse caso eu acho bem mais legível

@rafaelss deixarei como antes, até que pense uma maneira melhor.

if current_user.role? :admin
  @cases = @cases.of_product @product
elsif current_user.role? :employee
  @cases = @cases.of_product_accessible_by_employee @product, current_user
elsif current_user.role? :customer
  @cases = @cases.of_product_accessible_by_customer @product, current_user
end