~sigh
was hoping to see this fixed as well, alas
Just letting you know we did see this; it ties back into the way the oils work, so it's something we'll have to look at while redoing the oils probably. In the meantime, adjust loading and pressure to minimise/avoid it.
I typically use roller as a quick underpainting tool underneath the lineart layer, so going to the 'edit layer texture' attribute for the color draft layer and setting paper grain to zero for that layer only works fine.
maybe adding a way to ignore paper grain for this tool along with a checkbox for user to do so could be easier than globally reworking the way oils operate (unless an update for those has also been considered.)