raze -|- You can both raise and raze the roof, but if you raze it, you'll be sad when it rains. Raze or "to destroy" is always spelled with a z.  

receipt -|- Like pneumonia, the –p in receipt is silent, but necessary. And don't worry, this word follows the ‘-i before –e' rule 

reign -|- Excessive rain will reign terror on crops. Reign also reigns terror on the –i before –e rule, sorry, you just have to remember.  

relieve -|- You'll be relieved to know, this word follows the –i before –e except after –c' rule.  

renaissance -|- It may be easier to remember the history of the renaissance than to spell it. This is another of those big words you just have to memorize. Try breaking it up : ren – ais - sance 

rescind -|- You resend a letter, but you rescind an invitation.  

reservoir -|- Think of this word from it's origin, reserve; drop the –e and add the French suffix –voir.  

ridiculous -|- This is another word that is easier to spell if you remember it's root, ridicule; again drop the –e and add the suffix –ous.  

roommate -|- Spelling roommate is a lot easier than having one. Just combine room + mate and keep both m's. 

reference -|- Refer to the -e's in this word when trying to remember whether to put an -ance or an -ence at the end of the word. 

relevant -|- It's relevant to remember there are 2 e's followed by an -a in relevant. 

rhythm -|- Rhythm Helps Your Two Hips Move 

really -|- Another easy adverb. Just add an –ly.  

referred -|- refer – red  

repetition -|- There's definitely some repetition in this word. The e's, t's, and i's repeat, but are separated by one letter each.  

restaurant -|- rest – aur – ant – keep in mind, the "aur" makes an "er" sound.