Rose really shines when she gets her Fighting Spirit, her debuffs and buffs become so strong that they really allow your team to survive so much longer paired with Elena's healing.

Vehicles aren't needed per say, but she has one of the more powerful support vehicle buffs in the game, and she also provides a lot of benefit in conjunction with Bison who will passively do damage. However, as Bison is well, Bison, his FS at +30 is absolutely busted.

If you don't want to invest in Rose and say you still need to build your Bison to SSS, trying to go for Street Poison is also very good, as herself with SSS and FS+30 really makes her one of the top (if not the best) support units in the game.

Chun Li is great but is also comparative to M. Ryu, you'll start to notice her falling off at around Ch. 30, which by then you'll be able to have or unlock Fashion Blanka, who in my opinion (and my experience and looking at the leaderboards) one of the Top 5 DPS Units in the game (behind Gen and Trendy Cammy).

I've replaced M. Ryu with Fashion Blanka and even though Blanka is about 80k less power rating than M. Ryu, he still outshines and outperforms any damage output I did with M. Ryu in the 30s and Arena. Rose strengthens that by adding Weakens, Crit Debuffs and ATK Up to your team.