stoned as a rock

When you are so high that you are literally a rock

I smoked 6 blunts and cant leave my bed. I am as stoned as a rock

Heart of Stone on the Rock

The world's worst cocktail: tap water poured over a solitary ice cube.

Can also refer to someone in a position of authority not giving their mates any breaks

JJ: hey did you hear Bungle is now running the Balham Tup?
Pat: sweet, did he hook you up with free booze?
JJ: no way man, he'd even charge me for a Heart of Stone on the Rock!

I'm stoned cause I'm rock hard

I'm stoned cause I'm rock hard is used when somebody mentions that you are "stoned" so you respond by saying you have a raging boner.

Random bot "Bro's stoned "
Guy "I'm stoned cause I'm rock hard"

stoned as a rock

When you penis is harder than hard.

Alex: Hey your penis is hard.
Drew: Yeah, it's stoned as a rock!