Rolling a 172 - or not

In article ,
Big John wrote:

[...]

3. An aileron roll is just laying the aileron over (normally full
aileron) and letting bird roll. Depending on type of aircraft (fighter
or GA) the nose makes a circle around a point. Fighters can do at
cruise with little or no nose above the horizon. GA requires a start
with the nose above the horizon due to slower rate of roll and bird
ending up nose low because no other control input to hold nose up
while inverted is used

The question for me -- and what prompted my earlier posting(s) -- is
whether it's possible to do a standard aileron roll and get negative G's
(or non-positive G's, to be precise). The puny GA planes I fly all have
positive G forces all the way around an aileron roll (unless you do
something funny with elevator and / or rudder), but is that true of all
aircraft?

Hamish