The rock rules are terrible, I would even say pathological. They are:
* The rock is worth twice the big blind
* 5️⃣ The player with the rock must post it as a straddle immediately regardless of position
* Action preflop always starts UTG 5️⃣ unless the rock is UTG in which case it starts +1
* If a player in the blinds has the rock, 5️⃣ it replaces their normal blind