When it comes to rotating sprites, it’s a quite difficult task given the resolution of the sprites. I’ve implemented an algorithm called RotSprite that rotates low resolution images in a way that is more aesthetically pleasing than traditional rotations. You can add it as an extension with the url: https://github.com/ChaseMor/pxt-arcade-rotsprite.
Here is an example of this extension
It’s a pretty basic implementation though. There’s definitely some optimizations that can be made.
For an asteroids-type game, it would probably be better to use vector graphics. I started an extension for this, but ultimately became busy with other things.
I can revisit and finish both of these (especially since they only work for JavaScript) if there is demand for them though.