figma plugin rotation function based on https://gist.github.com/LukeFinch/d3c93d79a9dcd6970358be1d17838318

figma-rotation-function.js

function setRotation(node, angle){

  let { x, y, width, height, rotation } = node;

  const theta = angle * (Math.PI / 180);
  const originTheta = rotation * (Math.PI / 180);
  const centerX = x + width / 2;
  const centerY = y + height / 2;

  const originX = (-Math.cos(originTheta) * x + y * -Math.sin(originTheta) - centerY * -Math.sin(originTheta) - centerX * -Math.cos(originTheta) + centerX) - width;
  const originY = (Math.sin(originTheta) * x + centerX * -Math.sin(originTheta) + y * -Math.cos(originTheta) - centerY * -Math.cos(originTheta) + centerY) - height;

  const originCenterX = originX + width / 2;
  const originCenterY = originY + height / 2;
  
  const newX = (Math.cos(theta) * originX + originY * Math.sin(theta) - originCenterY * Math.sin(theta) - originCenterX * Math.cos(theta) + originCenterX);
  const newY = (-Math.sin(theta) * originX + originCenterX * Math.sin(theta) + originY * Math.cos(theta) - originCenterY * Math.cos(theta) + originCenterY);

  const transform = [
    [Math.cos(theta), Math.sin(theta), newX],
    [-Math.sin(theta), Math.cos(theta), newY]
  ];
  
  node.relativeTransform = transform;

}