The radio button labels currently imply that the options can be applied to multiple roles that are selected. However, when you actually select multiple roles, the radio button section disappears entirely.
In reality, the radio buttons only apply to when you've selected only one role, so the labels need to be changed to reflect this more accurately.
The attached patch changes them from these:
"Create random groups from members with selected role(s)."
"Create a separate group for each role selected."
"Create random groups from members with the selected role."
"Create a single group for the selected role."