This is a really solid concept and I'd love to see it developed further. I really love the core mechanic of rolling for which towers you get to place, but being able to lock the ones you liked.
I didn't really use the upgrade feature tbh
I'd have loved to see some tooltips on what the towers do when you mouse over them, because on my first roll I had no idea what anything was.
I was a little surprised to see that all my towers were gone each round, I've have liked to build up a defense rather than it being 100% what rolls I get that turn.
Overall, great work, this has a lot of potential