I fly with a carryon only however just in case there's no overhead space for the roller I have the following in my personal bag (a medium timbuk2 messenger bag):

Freedom baggie
Sampler sizes of various meds (NASIDs, anti-histamines, anti-diarrheal, anti-gas, cough drops, pepto bismol tabs, acid blockers) all fits into a small sandwich baggy!
water
energy bars
pens
paper
travel notes
laptop (macbook)
spare battery
power brick
camera
headphones (etymotic hf2 for iphone)
earplugs
kindle
chargers (laptop, camera, phone)
magazine or two

Just in case:
1 shirt
1 pair boxers
1 pair socks

Jacket in overhead.

Often I'll repack the just incase once I'm on board the last leg so everything fits under the seat ahead.
Non essential cables, dongles, extra non-essential papers all go in the roller. However it's mostly clothes and the rest of the toiletries.

I'm a pretty efficient packer and have had two week long international biz trips in the last 3 months with this set up. Last year I did a 4 day conference (biz casual) in just the messenger, it was pretty tight and a washed an outfit.