Tire sealant - A lot of automotive stores sell tire sealant, and thank goodness because tire sealant is perfect for patching up a flat until you can make it to your nearest mechanic or tire shop.
Tool kit - You should always bring a tool kit along in case there are issues that require operator level repairs.
Flashlight - Bring a flashlight along to provide light, or possibly signal for help.
These items will serve well in your personal roadside kit, you can never be too safe, so always be thinking of items that will be helpful to you in case of a less than fortunate situation.