Try riding three days a week, monday, Wednesday and Friday as fast as you can for an hour uphill, and on Tuesday and Thursday RUN as fast and as long as you can.
Riding up steel hills really makes a difference compared to riding fast flat roads. Last summer I started going up steep hills I had to take in low gear on a mountainbike, keep spinning and stay seated so the rear tire would not lose traction and stop me, they were long hills too where my heart was pounding and I could not breathe any harder by the time I got near the top, so I could not have done any more without having my heart burst or maybe passing out. This really made a big difference when I got onto a road bike and hit a hill, I was able to take the hills in a much higher gear and at a much higher speed than at the start of the season. And running puts muscle on the legs and core that riding a bike just won't. I also started riding up hills on the road in a high gear while standing up as fast as I could.
I think this hard type of workout made me much stronger and faster than just riding on the road five or six days in a row. And the weekend off really helps the muscles recover, as when you jump on the bike Monday you will be able to go REALLY fast, the fastest you will be able to go all the rest of the week if you are hitting it hard.
IN the winter I was riding a road-bike on a trainer with as much resistance as I could stand, pedaling as hard as I could for a half-hour to an hour, alternating with days of lifting weights, toe-raises and squats, also stuff for the arms. I live where there are very harsh winters where it is impossible to ride outside in many feet of snow and far below freezing, so that is the best I can do sometimes. A friend of mine lost fingers riding the winter here to frostbite.....