Whipper Root Tubers and Night Dragon's Breath are instant heals and mana regeneration each on its own seperate 1 minute timer. These come in handy for any and all raids but expecially during the Ragnaros fight when you are using your potion cooldowns for something else like Greater Fire Protection Potions(duh).
In order to farm them you will need to talk to Maybess Riverbreeze in Southern Felwood to begin a small chain. Find her directly east of Emerald Sanctuary and north of the small lake there. Once you are given a quest to carry a beacon while killing things in Felwood, you will be ready to collect Tubers. Heres a fun map for you to follow aswell:
And to make your existance that much easier, Try downloading the FelwoodGatherer add on found here.