Yes, you can make vegan trifle. The jelly is set with agar agar, so do pay attention to how many grams of agar powder you put in, otherwise it sets as solid as a rock, which isn’t what you want in a jelly. There is also a split between those who think the jelly should be on top and others who believe the jelly should be the bottom layer. One could write a PhD on this kind of thing.
Sour cherries aren’t easy to get hold of, but you can buy them tinned, in a jar or frozen from Middle Eastern suppliers.
As you assemble, make sure the coils of Swiss roll can be seen through the sides of the glass bowl. This should be a billowing froufrou dessert in red and white.
You will need a Swiss roll tin, or a baking tray plus non-stick baking parchment.
Obviously the Swiss roll and the jelly can also be served as separate desserts.