Mark Rippetoe's books are a pretty good reference. I've lifted weights for track but that ain't road, but in winter it's valuable. Means you're not out riding in the dark and cold but you still get some benefit, and IME there's no harm starting the season strong. The trick is to train till there are no more on the bike benefits to be had - in my last programme I phased out gym work for sprint work, with a maintenance session once a week in the early part of the season which eventually I dropped altogether.
There are better road riders here than me, and they have good counter arguments. It's up to you where you strike the balance, oh and BTW I race at around 185 - 190, so I'm heavier than most roadies. I train my strengths I suppose you could say.