2013 Kona Jake, 2008 Kona Major Jake, 2013 Kona Jake the Snake, 2006 Kona Kula, 2012 Ridley Excalibur, 2008 Surly Long Haul Trucker, 2001 LeMond Buenos Aires
You don't really need a road bike to become a cyclocross bike to ride it on gravel roads and dirt paths. If you can fit a CX tire on it, it's probably OK. Those kinds of roads tend not to be much worse than badly paved roads. Small tree roots are probably easier on a bike than a nice big pothole.
Go find yourself a set of cross tires that fit your bike and the style of trail you want to ride on. If you have 700c wheels it should be easy. If you have 27" wheels it won't be so easy. For my 27" wheels I found some club roost tires that worked very nicely. They have even held up on normal pavement which is typically horrible for cross wheels.
Your biggest concern will be weight on the rear wheel. just check spoke tension and tire pressure often. Use your current rear wheel and just replace it if its not strong enough.