Parksey wrote: Also, I'm about halfway through Turtle's Rock, but I've not got the Fire Rod yet. I've hit a dead end though and need one key to be able to progress to the mini-boss, but I can't find a key anywhere. How do you get in through the roof to bomb those worm things?
I got myself confused trying to type out a guide for you so here's GameFaqs to the rescue.
From the room the Dodongo Snakes are in:
Here, just avoid the Dodongo Snakes and continue up and left into the following room. In this room, jump over the lava-filled gap and stand on the middle platform. Defeat the Gels that appear, then jump over the second gap to the left and beat a couple more Gels. Then, unlock the door with a Key and enter that room. In this room, go down and left around the barrier, then take the Winged Arrows by using the feather to help, then go left into the next room. Here, just go left and defeat the Snake Ropes, then go up the steps that lead outside of Turtle Rock.
Outside, defeat a Mini Moldorm and a Crow, then climb the steps and take a Heart Piece. Then go back down the steps and go right across the bridge to the next scene. Defeat another Crow and continue right past the warp and to the next scene. Here, defeat a Shrouded Stalfos, and then go back inside the rock through the cave entrance you see. You'll be on a ledge above the "pit" of Dodongo Snakes.
Beat them by placing a bomb, then picking it up. When a snake is moving upward straight towards you, throw the bomb down and it'll eat it and get injured. Repeat that process until both snakes are destroyed and the treasure chest appears. Open it to get a Key.
Regarding the bolded part, hopefully you've already unlocked this door.