Roger's a lot different now he works with the stars (10)
I believe the answer is:
astrologer
'he works with the stars' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'roger's a lot different' is the wordplay.
'different' is an anagram indicator (letters placed in a different order).
'rogers'+'a'+'lot'='rogersalot'
'rogersalot' with letters rearranged gives 'ASTROLOGER'.
'now' acts as a link.
Can you help me to learn more?
(Other definitions for astrologer that I've seen before include "Compiler of star charts" , "Horoscope producer" , "Maker of horoscopes" , "stargazer" , "Studier of the supposed influence of stars" .)