I have been doing the Battle Tower, and throwing together teams that don't do amazing. I was wondering what roles I should fill. Please give examples for each roles.
You didn't ask on Smogon, so I asked for you.
With classic rules at least, I would say in general teambuilding isn't too different from what it's been in previous facilities, the biggest thing to keep in mind in this iteration being Leon's Charizard that you must have a solid answer to.
In Singles, you want to have 1-3 set-up sweepers supported by 2-3 mons that cripple the opponent by reducing stats or taking away moves (including PP stalling). These roles can overlap, Salamence for example contributes to crippling with Intimidate while being an excellent set-up sweeper.
In Doubles, things aren't as clear-cut because of the variety of possible strategies, but useful roles include: Fake Out user Tailwind / Trick Room setter Tailwind / Trick Room exploiter Intimidate user fast, hard-hitting attacker (effective 110+ base Speed) Focus Sash user Tank (Sitrus or Gen7 50% berry, or Poison Heal Gliscor, or Leftovers Leech Seed Celesteela/Ferrothorn...) Mat Block user (this means Greninja) * Tapu
There is still room for Doubles innovation even in oldgen facilities so I encourage you to build more; following a "formula" is often less effective than "inspiration" and teams that look good due to filling all the roles might not work at all in practice. There's a reason I gave up writing a Tree guide over just playing.
If you want BP, I would prioritise getting KOs and winning quickly over winning the most consistently. At least in SwSh. Because you don't get rewards for a long winning streak, you're better off winning 90 matches out of a hundred than you are winning ninety-nine in battles that take twice as long. Dynamaxing also slows battles down, so try to avoid it.
For doubles, I'd recommend having speed control on one mon, and a strong fake-out user as your other lead. Maybe make sure one of your leads has screens to be safe, or something like screech or fake tears to guarantee you KO any problematic mons turn one.
Keep two strong wallbreakers in the back that hit things that resist your leads. Also make sure you have something that can OHKO Leon's charizard in the back.
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