The roastburger is weak. It certainly doesn't satisfy any sort of real burger craving. However, instead of an overpriced fountain drink, you can buy a Jamocha shake as your drink and get the weakburger for free.
A word of warning though: they just phased out their regular Jamocha shakes and they now only seem to serve the more expensive swirl shakes, about $2.79 for a 20oz.