  The Rosette HH1 jet is a collimated flow immersed in the strong UV radiation
field of the Rosette Nebula. We investigate the physical properties of the
Rosette HH1 jet using high-quality narrow-band images and high-dispersion
spectroscopy. The new images show that the axis of the jet is not precisely
aligned with the star near the base of the jet. The high resolution of the
spectra allows us to accurately determine the contributions from the \ion{H}{2}
region, jet, and star. The appoaching and receding sides of the expanding shell
of the Rosette Nebula are at heliocentric velocities of 13 and 40 km s$^{-1}$,
while the jet reaches a maximum velocity offset at a heliocentric velocity of
$-$30 km s$^{-1}$. The [\ion{S}{2}] doublet ratios indicate an electron density
of $\sim$1000 cm$^{-3}$ in the jet and $\le$100 cm$^{-3}$ in the \ion{H}{2}
region. With a careful subtraction of the nebular and jet components, we find
the stellar H$\alpha$ line is dominated by a broad absorption profile with
little or no emission component, indicating a lack of substantial circumstellar
material. The circumstellar material has most likely been photo-evaporated by
the strong UV radiation field in the Rosette Nebula. The evaporation time scale
is 10$^3$ -- 10$^4$ yr. The Rosette HH1 jet source provides evidence for an
accelerated evolution from a CTTS to a WTTS due to the strong UV radiation
field; therefore, both CTTSs and WTTSs can be spatially mixed in regions with
massive star formation.
