Add a rootpath value to your keystone templates

keystone-rootpath.js

var path = require('path');

exports.assignRootPath = function(req, res, next) {

  var locals = res.locals;
  var rootPath = "";
	
  req.path.split(path.sep).forEach(function(item){
    if(item) {
      rootPath += "../";
    }
  });
	
  locals.rootPath = rootPath;
	
  next();

};