viewtopic.php?f=222&t=20727&p=139085#p138952
Going from that...
It's always been my understanding that familiars are 'animals' in the spirit world, hence the shaman's ability to revive them if they get killed. Summoning them gets done by someone entering the SS, wanting a familiar. They may know what they want or they may have had strange dreams with an owl in them or they may be seeking any familiar who'd have them for a host. I say host, because the person with the familiar becomes the familiar's anchor through the bond. They are not 'found animals' in the woods or one's pet dog. A familiar is a spiritual being that manifests through summoning, anchored to the world by their level of bonding to their host. So, a potential host is at the SS and the SS-clerk takes out a token that is used for summoning. The two hold the token and the host either envisions the familiar they have in mind or lets themselves be open and their energy flow to attract one to their essence. The SS-clerk uses the token to then form a bond to the spirit world, to help traverse into it and seek out the familiar in question. This can be done just mentally and as a given, or descriptively with their essence being there and interpreting the world as it appears to them, like shaman do. In either case, once the familiar is 'found' the SS-clerk then begins the anchoring and bonding ritual based on the bond level paid for. This causes the token to either break, dissolve or in some cases transform and magically no longer exist with the familiar in its place, now tethered to the world.
I honestly have never heard of rolls being needed nor seen them done to obtain a familiar. Like Farvel said, it's not anywhere on the site or MB that we can see. Many of my chars have gotten familiars from others, and it was never performed with rolls.