You can use the Preview.app to perform that task.
Create a new service called RotateLeft like this:

and paste this code:
on run
tell application "System Events"
key code 36 -- Enter --> Open rename field
delay 0.1
key code 0 using command down -- command+A --> select all to include extension
delay 0.1
key code 8 using command down -- Copy name to clipboard
delay 0.1
key code 36 -- Enter --> Close rename field
delay 0.1
set fileName to the clipboard as text -- retrieve file name
delay 0.1
key code 31 using command down -- Command+O --> Open file (Default application must be Preview)
delay 0.1
repeat until exists window fileName of application process "Preview" -- Make sure image is open
delay 0.1
end repeat
delay 0.1
key code 37 using command down -- Command+L --> Rotate Left
delay 1 -- If you are using really big images rise this value so the program can do the task
key code 13 using command down -- Command+W --> Close image (use code 12 if you want to Quit every time)
delay 0.1
set the clipboard to {} -- erase clipboard
end tell
end run
Before using the Service you must allow Preview under Security/Privacy/Accessibility like this:

You can change the delay values to fit your needs. Also add a shortcut under Preferences/Keyboard/Shortcut/Services. Remember to duplicate the service using key code 15 (Command+R) instead of key code 37 to do RotateRight.