OKAY so the rock is an unintentional huge red herring, before you progress in the story, you try to go to lavaridge, you're blocked by the rock, and you're like "oh I'll unlock this area once I learn strength" but you don't actually unlock strength for a while and you need to get into the town NOW soooo.
So actually, upon doing all of the story stuff, like miles away on the upper left part of the map, you gotta go back to that area in route 112 just south of the fiery path cave, and those two guards that were inexplicably blocking the path to the building next to it will be gone, and what they were blocking is actually a tram you can use to skip right over the rock and straight into lavaridge town