  We present the results of a comprehensive Spitzer survey of 69 radio galaxies
across 1<z<5.2. Using IRAC (3.6-8.0um), IRS (16um) and MIPS (24-160um) imaging,
we decompose the rest-frame optical to infrared spectral energy distributions
into stellar, AGN, and dust components and determine the contribution of host
galaxy stellar emission at rest-frame H-band. Stellar masses derived from
rest-frame near-IR data, where AGN and young star contributions are minimized,
are significantly more reliable than those derived from rest-frame optical and
UV data. We find that the fraction of emitted light at rest-frame H-band from
stars is >60% for ~75% the high redshift radio galaxies. As expected from
unified models of AGN, the stellar fraction of the rest-frame H-band luminosity
has no correlation with redshift, radio luminosity, or rest-frame mid-IR (5um)
luminosity. Additionally, while the stellar H-band luminosity does not vary
with stellar fraction, the total H-band luminosity anti-correlates with the
stellar fraction as would be expected if the underlying hosts of these radio
galaxies comprise a homogeneous population. The resultant stellar luminosities
imply stellar masses of 10^{11-11.5}Msun even at the highest redshifts.
Powerful radio galaxies tend to lie in a similar region of mid-IR color-color
space as unobscured AGN, despite the stellar contribution to their mid-IR SEDs
at shorter-wavelengths. The mid-IR luminosities alone classify most HzRGs as
LIRGs or ULIRGs with even higher total-IR luminosities. As expected, these
exceptionally high mid-IR luminosities are consistent with an obscured,
highly-accreting AGN. We find a weak correlation of stellar mass with radio
luminosity.
