I mean, one of the solutions to the tree and spikes on his back, is if the potion also has some rubber/cartilage in those part of the bodies, so this way you don't have to worry about having trouble rolling their inflated bodies. So there is a way to do it, you just have to make another potion to make even the things sticking out, like this tree here, easier to roll the body. In my opinion, the spike and tree should sink into the body as well, not just the arms, head, and feet.

Would need to give him a Rubberize Potion or Pool toy Potion to make them squishy.
I thought about them sinking in. But after considering how the potion works and how their on the surface of his shell. It Looks better with them sticking out. And to make it a different effect than the Ball Potion. This one just inflates your body, though a tail is absorbed and flattened into the ball here.

Hmmmm....Too bad the tree can't be cut or something...Or flatten and flexible...Oh well.

I mean, the thing about body inflation, which is the same as blueberry inflation and other potions, it could be modified to the person's content. In other words, it can be heavily modified, to where it can be formed and done in any way shape or form, even if something's stick out of your body, when inflated like a balloon, or a blueberry, or another spherical fruit appearance.
But again, oh well, it was just an idea/thought I had in mind when it came to something like this.

Regardless, I still like it, even if it would be difficult to roll this inflated Torterra to some juicing room or deflation room or something. At the same time though, seeing creatures that can waddle can be very mesmerizing.

The potion only last 30 mins normally. Then he'll deflate back to normal. But he's so cute like this I might feed him a potion extender.

True....Again, I think you may need to modify the potion to where it can last 2 hours instead of 30 minutes...That's just me.