Here is my project bike:

The CA carbon is really stiff and light, which is about as good as you're probably going to get for a fast climbing bent. My Al TW-Bents is a tank by comparison. After letting a co-worker test drive mine, he went and bought a Carbon Aeron 2.0 and it was a slick bike.

Keep in mind, climbing on a recumbent is different (significantly so). Not necessarily better or worse, but the physiological work it very different.

I really like my velomobile, even though it's much heavier, because it doesn't really matter how slow I go, I don't have to worry about balancing.

So, so.

Are you looking for something faster than your Roubaix? If so, this is probably not that.

I'm more interested in comfort, but since there are a fair amount of hills where I live, perhaps something a little lighter than a Giro would be a better choice.

You can make a Giro a bit lighter with a carbon fork and a different seat that’s lighter. Not sure by how much. Tires and components also.

Someone once suggested that, for example, you want your bike to be 5 lbs lighter, it might be easier for the rider to lose 5 lbs. Just an example.

Old Giros were steel. New ones are aluminum and are lighter. If you're after light weight, stay away from the recurve seat. "Lighter than a Giro" would be a Corsa or something in carbon.