I am also a 5' tall female and finding a suitable road bike wasn't an easy task.
If you're looking for a a women's bike with the sloping/dropped top tube? Well, they were originally designed that way to accomodate skirts, and there really aren't any decent road bikes made that way anymore. About the only road bike I'm aware of that is, is the GMC "Denali", which is sold at Walmart for roughly $140--and I'd advise against it.
There are a few "comfort bikes" on the current market with that dropped/sloping top tube, but they're pretty heavy and they're really only good for cruising around town, 2-3 miles at the most.
WSD (Women specific design) road bikes are now made with a shorter top tube and narrower handlebars--so you don't have to stretch out as far or spread your arms as far apart to work the gears and brakes. Otherwise, the design is the same as mens' bikes, although bikes with a "compact design" generally have a slight slope to the top tube.
Good brands? Trek and Specialized are always a good choice, but there's so much variety out there and honestly, it's all really a matter of personal preference. (and I agree with the above poster who recommended you look for Shimano 105s components--which offer a good combination of quality and durability. The quality of the other parts on a bike equipped with 105s are usually also fairly decent.
As far as what size frame you should look for? It's not just a matter of your height, but body build and the overall geometry of the bike as well. At 5' even, 47" - 49" generally. It's advisable though to go to a reputable bike shop and get properly fitted, and test ride a few bikes, if possible. This may be difficult because most bike shops don't carry a whole lot of smaller road bikes--IF ANY! I ended up having to order on-line because I couldn't find a bike shop that carried any itsey, bitsey bikes with the level of quality I desired--and I looked for a very long time!
My road bike is an Airborne Titanium WASP, which is a women's specific design, 47" and weighs in at a whopping 16 pounds. I've never owned a bike before that came anywhere close in terms of speed, distance, and hill climbing capability. Truely an amazing bike, but unfortunately, no longer produced.
Best of luck!