In Temporal Flux:
- Go to Locations, select {000} Load Screen and click Events in the sidebar that pops up.
- In the next window, at label [0075] in an unhacked ROM, there's a MemCpy(Mem.PC1, { 00, 80, 80, 80, 80, 80, 80, 80, 80 }). That's the initial party setup. 80 values are empty, 00 is Crono, and the party members go in the order of Crono, Marle, Lucca, Robo, Frog, Ayla, Magus. So for Robo change 00 to 03.
Bonus possible future questions answered:
- At label [00E1], there's a SpecialDlg NameCrono. Changing this will give you a different name screen prompt.
- At label [00E3], there's a ChangeLocation to 1F0. This loads the overworld event scene with the birds and balloons.
Bonus answer to a more obscure question:
- If you download Warrior Workshop from the Temporal Flux plugins thread, opening that from the plugins menu will give you the option to edit character starting stats and stat growth. In the box labeled Hacks, there's a checkbox called "Any character can show ATB settings on first name screen opening." Originally, the active battle mode settings were tied Crono's name screen. Checking this will allow Robo or anyone else to call the menu if you haven't set it before.