@kallsenmi6 thanks for the question! We were able to confirm with Solitude that you don't need to make a reservation if you purchase a lift ticket at REI. Hope this helps, and that you're able to get some turns in soon!
Thanks for reaching out!
We have confirmed with Solitude Resort that they do not require a reservation when using a lift ticket purchased at REI. They did recommend that you take a photo of your ticket on your phone, as if it is lost they will need the number from the ticket in order to replace it.
Hopefully this helps, thanks!