How do I restrict payments using Purchase Orders to specific customer roles?

I've added several payment methods such as PayPal and Authorize.net. They all allow me to specify which customer roles are allowed to use them. For Purchase Orders, I was shocked to find it doesn't offer this option.  If there was ever a payment option you'd want to restrict from certain customers, Purchase Orders would be the first one on the list. Purchase Orders offered to customers who have a trusted relationship with the merchant.

If this isn't a bug, it should be.

In the Plugin List page, you can Edit a plugin, and use "Limited to customer roles"