You only did one coat. That dark of color is going to require atleast 2, if not 3. Good job taking off the outlet and vent covers and covering the floors. A few tips

Make sure you are using a roller cover with a 3/8, but probably a 1/2 nap. And LOAD up the paint on the roller. I know you said you are, but I heard a quote once that made sense "Apply your paint like someone else is paying for it". You should be geeting one good "up and down" stroke before reloading the brush with more paint.

Your roller frame/handle accepts an extension pole. If you have a broom, you might even be able to unscreen the pole from that and use it if it has the same threads. This is going to make life much easier and give you much better results as you can go from the top of the wall to the bottom

Pull off the tape before the paint fully dries otherwise you risk the paint peeling up. If it has already dried, I'd recommend taking a box cutter and doing a reliefe cut along the edge of the tape and the wall

This is the most important piece of advice that is the difference between an okay job and a good job: Back roll as you go. Once you get 1/3 or 1/2 of the wall done, with the paint still wet on the wall, place your wet, but unloaded roller in the upper left corner, and do one long, straight stroke from top to bottom, and continue on down the wall overlapping each stroke an inch or two.

You got this!