Pretty much the same as on the mtb - roadie lycra.
That said, the shorts (mostly the cheap nalinis from probikekit) don't have a very thick pad and the roubaix or coolmax longs (lusso) have more like double thickness of material, rather than a pad. Open legged shorts ? - a bit draughty for my evening commute, plus I'd rather nor get insects around my nether regions....
One thing I've found is that when it gets chilly, my knees suffer a lot more on the 'bent from windchill compared to on an upright. On the admittedly v cold fnrttc to Southend they were aching all night, and the kneecaps were still sore most of the following day. I've since bought some windstopper longs - tho' need to find some windproof kneewarmers as a tailpack backup. (Bib) knickers might be an alternative but the few types I've tried have had leg elastic way too tight - felt my calves were gonna explode
- not sure having a selection of varicose veins doesn't help..
On the jersey front...
zipped pockets in the back are ok so long as they're far enough to one side as to miss the seat pad when the zip pull's to the othermost edge (or fits a gap in the seatpad, as with one jersey)
Race-cut and/or jerseys with 3/4 or shorter zips produce less bunching across the belly - depends on the size of the belly of course, ymmv
I've a few tri-tops that work fine too, and a couple of De Soto trisuits (fairly cheap via a tri-shop on ebay) - they're good 'cos there's a thin pad and just one layer of material all over - they've also got a couple of small pockets on the thighs, big enough for a notes (currency or otherwise)/directions/train tickets..tho' they might get a little sweaty.