Can youuse road diesel in stead of kerosene in domestic boilers?

Sure it can, there are many home boilers that use #2 oil (road diesel) for heating. However, you must carefully study the boiler to be sure there are no negative consequences of changing the fuel. Kerosene has less heat content, is less viscous and burns easier than #2 oil. You may be able to change the burner tip orifice to compensate for this, but I would contact the boiler manufacturer to see if this is possible. You also may have to change the ignition system to adapt to the other fuel.