If the roadies blew past you on your hybrid it's not because they were on road bikes. It's because they've ridden a lot more miles than you and are in better shape. I know you're working on it, but just getting a road bike isn't going to do much for your speed over your hybrid. When I was losing weight in 2009 I started riding a mountain bike (hard-tail 29er) at around 350 lbs, and kept riding the crap out of it. I took the wide knobbies off and put on some beefy slick tires that were maybe 32mm or 35mm wide, and rode that for thousands of miles.
When I was around 275 or 280 or so I bought a used road bike for $450 and picked up maybe 2 or 3 mph for the same perceived effort, but that meant that instead of going 15-17mph on that mountain bike I was now going 16-19 mph on the road bike. Probably much of that gain was due to a change in position from fairly upright on the mountain bike to more tucked in as I rode the hoods on the road bike.
By all means, get a road bike and enjoy the hell out of it. Just keep the expectations real. It's mileage and improved fitness and endurance that's going to get you the speed you want most of all, and the equipment comes in second.