Having been sacked by Tottenham, former Chelsea, Manchester United, Real Madrid and Inter boss Mourinho was appointed as Roma manager in May, replacing compatriot Paulo Fonseca.
Mourinho's first competitive match in charge will come in Roma's Serie A opener against Fiorentina in August, and the Giallorossi made an emphatic start to their pre-season against Serie D side Montecatini.
Borja Mayoral scored a hat-trick, with his first goal coming after Carles Perez and Gianluca Mancini struck to put Roma 2-0 up.
Riccardo Calafiori netted a swift follow up and an own goal from Montecatini put Roma 5-0 ahead at the break.
Nicolo Zaniolo converted a penalty after Mayoral helped himself to a second, with the Real Madrid loanee completing his hat-trick after Nicola Zalewski and Amadou Diawara had got on the scoresheet.
Serie B newcomer Ternana is next up for Roma, which faces Serie C outfit Triestina three days later before rounding off its pre-season preparations with friendlies against Debrecen, Mourinho's former club Porto and Real Betis.