More gears.

And more discipline.

I have the same issue. I plan to ride near your numbers in a race, but on hills, I have a hard time keeping my power below 200 watts. When I'm not paying attention, I'm giving every hill 250+ watts until I catch myself. Most riding I do is flat. Usually only get out to hilly areas on group rides where I don't watch my power closely. Luckily my only race this year is New Orleans which is flat, but one day I'll have to figure this out as well.

It really depends on why you are spiking. As mentioned above "more gears" can be one solution, but only if the cause is a lack of short-enough gears to spin up the climb...or tall-enough gears to keep up the power on the descents. But, if you are just losing discipline on the first 3rd (or whatever) and "spiking to 300 watts"...then that's what you need to focus on. Gears won't fix a lack of focus/discipline.

If it were me, I'd be looking at the power trace over an uphill/downhill section and look at what you did. Do you see a spike in the first 3rd? Do you let off the gas as you crest the hill? Do you spin-out on the descent?

I don't know the course...but, rollers are notorious for encouraging you to hold the speed to get over the crest, which then encourages you to relax over the top...etc. If that is your case, it certainly takes practice to maintain that discipline. I have nothing but short rollers around me, so I get to practice that every time I ride.