I'll always say that rouge was a plant by a furry devs to corrupt my young mind…
I have too…

The only time Sega's ever really put any of Sonic's friends into the spotlight is when their experimenting with weird gameplay mechanics, examples being:
Knuckles Chaotix (Ring power/ Combi system)
Tails sky patrol (Constant flight and no Rings)
Tails Adventure (slower paced platforming with more emphasis on combat and exploration than speed)
Shadow the Hedgehog (Guns/Multiple story paths).
Dr. Robotnik's Mean Bean Machine (Localization of Puyo Puyo)