Back in the early 80s I did a fair bit of mid winter after dark roach fishing on the Dorset Frome at Wareham QWuay. More failures than successes and we soon found that maggots brought amazing numbers of tiny flounders (47 one evening) and elvers - both species long gone, even dace as well, using a float. In time I had more success using breadflake and some nights had big roach when anglers had blanked in the same swim all day. Many years later a handful of anglers fished the same swim night after night but success was an exception, and some claimed that the roach would reappear long after midnight not that I wanted to be on the river that time of night. Even on the nights when the roach fed the action ceased by 9pm though given that I would be staring at a computer screen the following day for 7 hours programming in the days of green on black screens overdoing it watching a betalight wasn't recommended. The very biggest roach rarely showed after dark when I fished though I had one or two very good ones and strangely roach just under 2lbs which rarely showed in the day sometimes turned up, maybe it was another shoal that visited at night? I did some legering but the rods were poor in the early days and only much later when armed with a top class carbon quivertip rod did it become easier to hit bites.
If the place is safe to fish then I'd try flake on a 10 with a little cage feeder with liquidised bread and see what turns up. Keep sessions short, 2 or 3 hours.