I might be misunderstanding what you actually want, but here's my way of handling round robin;
Personally, I use this for things like interrupts, death grip, etc., and it's fairly simple to set up.
1. Create new Action Target Group (ATG) -- For example "Interrupt"
2. Place characters you want in the Round Robin-group into the ATG you created
3. Go to your keymap and add a new mapped key (or edit an existing one)
4. In the mapped key, create (or edit existing) new step.
Next, if you want to round robin, say, the key "4", add a Key Broadcast that sends "4". The important part here is to target the ATG you created (in my example; "Target: All of "Interrupt""), and tick the "Round Robin"-box.
When you now press that key, it will target a random character in the "Interrupt"-ATG you created and make it - and only that one - send key "4". Of course, if you spam it, it will eventually send on all characters in the group.