While I don't main raid as Ret, I still set up an Inquisition weakaura for LFR. It's just an icon that's to the right of my character that has a timer on it, which stacks on top of other buff timers when they come and go (Avenging Wrath, Heroism, etc). I don't have too much of a problem tracking it where it is, since it's so close to my toon that I can keep an eye on my environment while I watch it, and I also watch other buffs in the same spot with my other toons.
I've been doing my rotation for that long that Inquisition just feels natural to renew, but aside from that I glance at the buffs above my Player Frame which is on the bottom left of my screen thanks to ElvUI.
World of Warcraft - Path of Exile - Hearthstone @Blsmonk