Possible Clues:

• He was 'thumb' critic!
• 'Sneak Previews' co-host
• "Sneak Previews" co-host
• Film critic with a famous thumb
• 'Life Itself' memoirist Roger
• He reviewed many pictures
• Roger with a famous thumb
• Critic with raised or lowered thumbs
• Siskel was his partner
• Colleague of Siskel and Roeper