Standover height varies with tire size too. My road bike and hybrid are technically the same sizes, measuring bottom bracket to seat tube and/or head tube lengths. But the standover heights are very different because the road bike wears 700x23 tires and the hybrid 700x42 tires. The hybrid has a longer top tube, chain stays and just feels more comfortable overall. The hybrid came with 700x32 tires and if I went back to those the standover height would be roomier.
Plenty of clearance to hop off the road bike saddle while straddling the bike without endangering Johnson and the twins. But it's a snug fit with the hybrid, depending on whether I'm wearing padded shorts or liners. I can put one foot down at stops, no problem.
Also depends on my shoes. Usually I wear casual walking/cycling shoes with fairly thick soles for platform pedals. With my thin-soled deck shoes it's pretty darned snug on the hybrid.
Main problem with the snugger fit on the hybrid is the bare brake cable running along the top tube. In real world riding conditions it would never interfere. But occasionally I worry about straddling the bike and the bare wire cable rubbing the paint. So next time I replace cables I'll use full length housings. The road bike already has a full length cable housing for the brake cable running along the top tube.
Most bike folks who see me with these bikes think the frames are a bit too large for me. But my legs are just a big longer than usual for a 5'11", around 33.5". And I have a long waist with narrow hips, so I tend to wear my pants low, which makes my legs appear shorter than they are. So if I depended on bike shop sales people who didn't do fittings, I'd be riding bikes a bit too small for me.
If you'd like a bit more standover room, try 700x23 tires on your Roubaix (I think 700x25 are stock) and you might find the standover height a bit more comfortable. There are even a few 700x20 tires around here and there, including some new/old stock Vittoria Corsos being blown out by a few online discounters ($15-$20 for what were once top shelf tires). And if you prefer softer riding tires that are still quick rolling and not sluggish, I can definitely recommend Schwalbe One V-Guards in 700x23, now available at half price most places for the 2014 models since Schwalbe has updated their One series lineup.