I might have been over thinking it Dave. The 15° requirement had me thinking of separate Type layers, which could easily be placed using Step & Repeat, but they would rotate around the centre of the circle, and be a PITA to rotate back to vertical. Note that I asked if the type had to be vertical, to which the OP answered 'Of course' but I wonder how literal that requirement is?
So I have been trying to think of ways to place intersecting guides at the relevant centre points for each of the 24 characters or groups of characters, without quite a lot of work.
Actually, having just tested that idea, it is not as much work as I thought it might be, because correcting the characters is going to use the same angles as when rotating about the centre of the circle, so if you drag it free hand to about vertical, the correct angle is going to be obvious, but still a bit of work, and I have no idea if this even what is being asked for.

BTW Even for Chris and I, 1.30am is on the late side (not so much for Chris) so I need to leave this thread to you. 
OK ,
I would do it in a slightly different way to Trevor. Nothing wrong with Trevor's method at all, but I use a different way to get the rotation
Start with your first line of text snapped to a guide.

Use the elliptical shape tool to create a circle (drawn out from the centre)

Duplicate your text layer (however many times you need - I've used 7 duplicates below to give 45 degree text)
Select the ellipse layer and the first duplicate and choose the move tool. The bounding box handles for the move tool will surround the entire circle and the rotation will be in the centre of the ellipse, i.e. the point from which you pulled the circle originally)


Rotate the handles by the required amount (in my case 45 degrees). Both the text and the shape rotate together.


Repeat for the other layers (each time selecting one text layer and the circular shape layer)

Finally flip the text on the layers as required (in this case those showing text on the left side)

You can now switch off the shape layer, and alter the text if you want different text at each point.
Dave