Enable MathJax in Roam (this goes in roam/js).

roam-mathjax.js

window.MathJax = {
  tex: {
    inlineMath: [["$","$"]],
    displayMath: [["\\[","\\]"]],
    processEscapes: true,
  }
};

(function() {
  var script = document.createElement("script");
  script.type = "text/javascript";
  script.src = "https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js";
  document.getElementsByTagName("head")[0].appendChild(script);

  (doTypeset = function() {
    window.setTimeout(doTypeset, 700);
    if (MathJax.startup) {
      MathJax.startup.promise = MathJax.startup.promise.then(
        () => {return MathJax.typesetPromise()}
      ).catch(
        (err) => console.log('Typeset failed: ' + err.message)
      );
    }
  })();
})();