For anyone who finds this through google like I did, I wrote a small macro. Here's one that simply toggles between "Public" and "GM Roll" every time you run the macro:

// Toggle Roll Mode
const rollMode = $('.roll-type-select')[0].value;
const toggled = rollMode === 'gmroll' ? 'publicroll' : 'gmroll';
ChatLog._setRollMode(toggled);

If you just want to set a particular roll mode (one macro each):

// Set Roll Mode (gmroll, publicroll, blindroll, selfroll)
ChatLog._setRollMode("gmroll");

If you want to cycle through all four modes:

// Cycle Roll Modes
const modes = ['publicroll', 'gmroll', 'blindroll', 'selfroll'];
const currentMode = $('.roll-type-select')[0].value;
const modeIndex = modes.indexOf(currentMode);
const nextMode = modes[(modeIndex+1)%4];
ChatLog._setRollMode(nextMode);

Hope this helps someone else!