We investigate two high-energy radiation mechanisms, the proton-synchrotron
and the electron inverse Compton emission, and explore their possible sign
atures in the broadband spectra and in the keV-GeV light curves of gamma-ra
y burst afterglows. We develop a simple analytical approach, also allowing
for the effects of Photon-photon pair production, and explore the condition
s under which one or the other of these components dominates. We identify t
hree parameter-space regions in which different spectral components dominat
e: (1) a region where the proton-synchrotron and other hadron-related emiss
ion components dominate, which is small; (2) a region in which the electron
inverse Compton component dominates, which is substantial; and (3) a third
substantial region in which electron-synchrotron emission dominates. We di
scuss the prospects and astrophysical implications of directly detecting th
e inverse Compton and the proton high-energy components in various bands, i
n particular, in the GeV band, with future missions such as the Gamma-Ray L
arge Area Space Telescope (GLAST) and in the X-ray band with Chandra. We fi
nd that regime II parameter space is the most favorable regime for high-ene
rgy emission. The inverse Compton component is detectable by GLAST within h
ours for bursts at, typical cosmological distances and by Chandra wit days
if the ambient density is high.