We discuss the production of primordial gravitational waves (GW) from radiative inflaton decay during the period of reheating, assuming perturbative decay of the inflaton either into a pair of bosons or fermions, leading to successful reheating satisfying constraint from big bang nucleosynthesis. Assuming that the inflaton $\ensuremath{\phi}$ oscillates in a general monomial potential $V(\ensuremath{\phi})\ensuremath{\propto}{\ensuremath{\phi}}^{n}$, which results in a time-dependent inflaton decay width, we show that the resulting stochastic GW background can have optimistic detection prospects, especially in detectors that search for a high-frequency GW spectrum, depending on the choice of $n$ that determines the shape of the potential during reheating. We also discuss how this GW energy density may affect the measurement of $\mathrm{\ensuremath{\Delta}}{N}_{\mathrm{eff}}$ for bosonic and fermionic reheating scenarios.