External Monitor in Portrait Mode with MacBook Pro

I've been searching around and found the "alt/option + command keys" trick, but doing this doesn't provide the rotation drop down on my Dell monitor (P2714H) (only offers to rotate on my MBP screen). Wondering if there's a workaround, or why this would be? Related to my OS X (10.8.5) or internal hardware (MacBook Pro (13-inch Mid 2012))? I would really appreciate any help!!