  This paper aims to recall some of the main contributions of Roberto Petronzio
to physics, with a particular regard to the period we have been working
together. His seminal contributions cover an extremely wide range of topics:
the foundation of the perturbative approach to QCD, various aspects of weak
interaction theory, from basic questions (e.g. the mass of the Higgs) to
lattice weak interaction, lattice QCD from the beginning to most recent
computations.
