Your rival will meet you outside of the gym and he will tell you to go to the city Library. Once you meet him on the last floor of the Library he will take you to Rowen.
Torterra learns Earthquake when it evlves, so try using earthquake if it doesn't do much damage or says "Its not very effective" then teach it Sunny day, and solar beam use sunny day first if you...
Byron will have a Bronzor, Steelix, and Bastiodon. Use Fire moves on Bronzor, and then Water moves on Steelix and Bastiodon. The only problem you should have with Bastiodon is Rest. It has a Chesto...
Your rival tells you to go to the library. Go to the library. If he never told you to go there, then there is probably something wrong with your game, or you need to do something else.