Make your sketch in your format of choice. Please note that if you use grid paper the grid lines will be taken into account when making sketches.
Next, import your sketch into an image editing software of your choice and clean up the image.
Next, open up Artroom and add the image as your starting image. On the right side open up Controlnet and select Scribble. Press "Preview" to see what the Controlnet is seeing.
Optional: If you see that the preview has taken anything from your source image, you can save it, load it into your image editing software of your choice and clean it up a bit more. You can then put it as your starting image and enable "Use Preprocessed Controlnet"
Adjust your Prompt, Model and other settings as you would usually do.
Generate a bunch of images and pick the best ones.
You can then take the image back into your image editing software of choice and add additional things the software might have gotten wrong to your image. Then select that as your starting image in Artroom. Don't forget to turn off Controlnet again. Play around with image variation strength. 0.2-0.5 is likely where you will get good results.
And with that you will get final results like this: