Struggling to understand rotation

I am spawning 50 random objects on the screen and I want them to all start off facing random different directions, then move forward until they are off the screen. I am trying to accomplish that by changing the x and y axis. However they always end up rotating on z as well despite it being set to 0.

I have seen several questions like this, I've read unity documentation and articles about angles, I STILL can't figure out how to fix what I'm trying to do and I'm wondering if maybe I'm just...

Struggling to understand rotation