Rosettes as a ... magic altar

[Rafal]

Any reason for selecting one of the 12 apostles with a wheel of fortune?

To pick your chosen apostle, by random or divine event, depending on your worldview 

Then there are many possibilities:
- you have to pray to that apostle
- at the moment of selection you automatically "get" protection and blessing of that apostle
- you get some personal message or fortune telling from that apostle, with magician acting as a medium or simply reading it from the book

In the manuscript with a wheel I don't see such messages but here is a similar thing from another manuscript. It contains pages with different sages, like Solomon, Abraham, Isaac, Aristotle, Avicenna etc. and they all have personal prophecies for you

Here is Isaac for example. First you get him out of the other guys by wheel or dice and then you probably choose some answers the same way.
   

[*]1.The trade / purchase will not go through.
[*]2.His enemy will not succeed.
[*]3.He will perhaps [succeed] in this matter.
[*]4.He wins / gains nothing on the goods.
[*]5.Much sorrow lies along the good path / because of the goods.
[*]6.The miserable / exiled one comes with great hardship.
[*]7.The maiden will live in poverty.
[*]8.The short-lived child will be greatly mourned.
[*]9.The woman gives birth to a little boy.
[*]10.The red-haired woman gives birth to nothing but little girls.
[*]11.Through the earth it will be ground / worked.
[*]12.Through poverty it comes to measure / moderation.
[*]13.Through love [one] will die.
[*]14.Those long granted / looked for will not bring heavy gain.
[*]15.Dignity / honor will not weigh heavily on him.
[*]16.The friendship of his lord does not fail him.
[*]17.He will not become a joyful host if he suffers / leaves.
[*]18. There is hope in the trade / transaction.