I think it's a decent idea, but it felt like I had no incentive to use the role changing mechanic at all. I kinda relied upon shooting fireballs and dodging enemy projectiles instead.
The sounds/music were too quiet for me even though I had the volume pretty much maxed out everywhere. Regarding the graphics, if you're going with pixel art style, I'd suggest keeping pixel size consistent everywhere; and the letter spacing on the ability selection screen is all over the place which makes it hard to read.
I liked the particles and damage splashes on enemies, but the screenshake, I think, was sometimes applied even when there was no apparent reason, which made it a bit distracting. Perhaps some off-screen enemies were doing their thing or whatever.
These remarks aside, good job on the game!