Glad you're enjoying it! You could use any cooked fruit as long as it's not too liquidy. Adding any water at all will make the ice cream icier and less creamy. So you could roast apples, pears, grapes, peaches, nectarines etc instead of the rhubarb and my roasted strawberries would be great in it too https://avirtualvegan.com/vanilla-roasted-strawberries/
Have fun experimenting!

Hi Jim, It is supposed to be 2 tablespoons. That is a lot, you are right but it is what gives it the custardy flavour. It isn't essential though. If you omit it or don't use so much you'll just have rhubarb ice cream and not rhubarb and custard!