Kalista and Aurelion Sol can have support as their secondary "roles".
First, let's look at Kalista:
Zyra and Ashe have support secondaries because they have vision, Ashe has her Hawk and Zyra has her seeds. Leona has supp secondary because she has a passive that makes allies auto attacks do better. Kalista has an even better vision ability, and an ability to save her ally from danger, finished with an ability to buff allies auto attacks, so she could have supp secondary.
Then, Aurelion:
The reason for Sol is quite unnoticed but bear with me. Syndra has support for her secondary since she has a knockback, but Aurelions ult does the same thing, so I feel like Sol could have support as his secondary.
Could this be a possible way to fill in the secondary roles for Sol and Kalista?