Riding in the rain is fun! There will be fewer drivers and bikers on the road.

If the road bike has very smooth tires, it's probably not a good rain bike. You want some tread for control. Fenders help keep you dry. I also have a rain jacket that's comfy even if it's very hot out and raining. I also like lights in the rain so cars can see me better. Just like with a car, give yourself more space to stop in the rain.

Now, go out and get wet (just not in a thunderstorm please, lighting strikes are too much excitement for anyone)