As you are not in an operational low flying area it must have been above 250 feet. The steep climb and use of reheat suggests you witnessed a practice low level abort, which being a safety-critical manoeuvre would justify the (normally-prohibited for noise abatement) use of reheat at low altitude. And I doubt it was a twinkle roll you saw, more like a wing over to arrest height gain once above safety altitude.
Wouldn’t want anyone getting into trouble.
