Please fix this ridiculous bug.

That's sixty extra pounds of dragon bone and dragon scale wasted because I can't sell (or even drop) these things...

QUEST ITEMS are weightless, they are always weightless. They may claim to have weight but they don't actually contribute to anything. The extra weight is from your potions, ingredients or some other assorted items. The same flag that prevents you from dropping and item also makes it weightless.

Empty your entire inventory into a container and you'll discover the scrolls are weightless.

*If you sided with Dawnguard(and only Dawnguard) you can sell two of scrolls to the Moth Priest. If you sided with the vampires then you're stuck with two weightless items in your inventory. The Dragon Scroll can be sold to http://www.uesp.net/wiki/Skyrim:Urag_gro-Shub presuming its already been used in Skyrim's Mainquest no matter whose side you chose.