I don't know if there's one claimed to be equally good for both species. VDE Expo is a tried and tested tench favourite. It's a red groundbait, and it has often been noticed that tench have a liking for red baits - red maggots, dyed corn etc. It's not cheap, but I cut mine with some brown crumb, and often feed a couple of balls to kick off a tench session.
There are lots of groundbaits aimed at roach ( and roach anglers) from heavy, sticky mixes that will carry feed like casters to the bottom in deep swims and rivers, to very light, fine, often dark mixes for less gung-ho styles on waters that need a less aggressive approach. For most roach fishing on shallow to medium deep stillwaters, I rarely use groundbait and prefer to loose feed hemp, casters, maggot or whatever.
I like liquidised bread in a cage feeder with flake for river chub, and some anglers use fine bread groundbaits with punch for roach. It's a bit specialised as it's easy to get the texture and the amounts wrong. The chub approach, come to think of, will probably catch carp and bream on your favourite pool, and hair-rigging punched out discs of bread makes a good stay-on hookbait.
I suppose it's a bit unpredictable, til proven one way or another, what will work. On one of the places I fish, the bailiff feeds a weird mix of liquidised bread laced with maggot, cubed meat and sundry other ingredients. I found him chopping up some tripe to go in it one day. I wouldn't dream of throwing this mix into my swim, but he regularly catches big roach.
