Proper glue to adhere laser printed paper to glass beads
There is a pretty big ‘cabochon’ crafts movement that sounds a lot like what you are talking about: Flattened glass bead + acrylic emulsion glue + laser print + backing.

The first video I Found on YouTube advised Modge-Podge Dimensional Glue, but I have no experience with the product, and would recommend an acrylic gloss medium, which will dry clear. DO NOT ADD WATER, you will only create wrinkles.

Here is the process: 


Trace out the exact size of your paper backing and cut it out. Do not touch the surface of the print with your fingers.
Wash the glass with rubbing alcohol, let air dry. Do not touch the back where you will apply the glue.
Apply a drop of the gloss medium to the back of the glass. 
Spread it out and make sure that there are no bubbles.
Place the paper on the glass with the printed side to the glue.
Press it down firmly and let dry. (30 minutes - 60 minutes)
When dry apply a second coat to the back of the paper to seal it (and especially the edges) and let dry.
Now apply third coat and attach magnet. Let dry. If you are feeling adventurous you can add the magnet without waiting for the medium to dry the second time.


A bit of extra advice: try not to use too much red in your design, because red dyes and pigment inks fade over time due to sunlight / UV exposure. I have experienced this in laser, some offset and most ink jets - even the 10-color art print versions. The only options you have are museum glass (that will reflect UV) or UV blocking acrylic emulsion. I use Sennelier Gloss lacquer with UV protection.