I’d guess 5 years old, possibly 4.  
Ime a Roman nose will usually start to show at age 5, Iv never seen one on anything younger.  This guys just starting to show, but does still have a good dish in his forehead. Ime after 5 years they trend to get thicker in the forehead and less of a dish. 
I’d guess 5 years old.   Sorry I’m no good at scores, but he does have room to grow.