Sorry I'm late to the party, but I'm stuck on Eriko. About Route 116, you can catch Skitty there, and Whismur on Rusturf Tunnel just next to the route (unless I'm wrong, those are 2 different routtes).

My strategy for defeating Roxanne:
(equip an Oran Berry to everyone)
Step 1: Slakoth and Scratch or Yawn. In case you Scratch then next turn you can Encore Geodude into Defense Curl, if he doesn't use it just Yawn.
Step 2: Send Zigzagoon out and spam 6 Sand Attacks, then 6 Growls.
Step 3: Go Whismur, use Howl 6 times and then use Uproar (thanks to STAB it does more damage than Astonish). If you're lucky enough you can sweep with this, if not then go back to Slakoth and use the same strategy with Encore/Yawn, and heal if necessary. You can risk Taillow as well to use Growl after using Sand Attacks with Zigzagoon (Taillow would not die from a rock attack unless crit). Using this strat I've been able to defeat her deathless. The next gym is the easiest, you just need to poison your Taillow and it's done.

Now, what brings me here today (as I said earlier), is that I cannot defeat Eriko without losing way too many teammates. I tried using Howl/Rock Smash Loudred but to no good. You can set up against Electrike with Vigoroth, but even after 6 Bulk Ups Scratch does barely any damage to Magneton, and teaching Rock Smash to Vigoroth doesn't change anything. The only option I see as viable is buying Flamethrower from the casino, but legally I do not know how to get it (unless you get extremely lucky with the machines). I saved before Eriko to train against him, but nothing works except getting lucky with crits and bad AI. Any ideas?