LOOKS LIKE THEY REMOVED THE LINK TO THE SPECIAL OFFER FROM THE ITEM PAGES, Deal is now dead.
Diablo 3 is on sale for PC at 19.99 at Best Buy, if you look in special offers it says when bought with ROS it would take $20 off, theoretically makeing it free. It doesn't work automatically that way, but I called in and after a wait they took $10 off each one to account for the $20.
This make Diablo 3 ($9.99 before GCU, and ROS $29.99 before GCU). ($5.99 and $21.99 after GCU) it depends on how they take that $20 off what your final prices might show, they might end up listing Diablo 3 for $0 and RoS for full price, or take the $20 off RoS but leave Diablo 3 at regular price. This is just how the rep who I got did it. However, there should be no reason not to honor the special offer.
YOU WILL NEED TO CALL IN!
Press 0 at the first list of options "Press x for x and such", then press 1 for sales and product information, inform them you wish to place an order, and then give them the item SKU for either, then direct them to the special offer link to save $20 and explain how it is not working automatically on the site like it should, and then they should be able to manually adjust it.
*If you are GCU, make sure you give them the email address associated with your best buy account, and it should take your GCU off automatically in the cart, MAKE SURE THEY TAKE ANY $ OFF THE GCU PRICES!
Grand total was $27.98 before tax for me.
Diablo 3 PC (Base game)