IS it possible to set an Approval process to be approved according to a role and not a specific user?

Thinking out loud, just dont use the next approver field in your workflow. Instead, in the action where you add button for the approve and reject button, have a condition whereby the buttons are only exposed for the user role required. I've not tested this, but I reckon this will work quite well.

@Mika Hakkinen Sounds like a good idea, I will check this. Thanks

Yes this is possible and common. Use the User Role field as a condition on the action and select the role(s) you want access the button to.