The only way to get through Rock Tunnel in Pokemon Red, Blue or Yellow is to defeat all the trainers one by one. Rock Tunnel is the only way between Routes 9 and 10.
There are no treasures to search for, only trainers to fight. To begin, if the player has a Pokemon who knows Flash, then it can be used to light up this dark area of the game.
Potions, repels and escape ropes will be helpful in this area. There are fifteen trainers to overcome, along with items to gain, including a revive and an escape rope. At the end, a young character will offer to teach a Pokemon Rock Slide, an intimidating attack.