Bielsa is known as much for his fiery temper as his acclaimed coaching skills and has been christened “El Loco” – the crazy one.
The Argentinian’s career has been littered with controversial moments and bitter bust-ups and he quit Lazio just two days after joining the Italian club in July 2016.
But Roberts, who could win a fourth Wales cap against Denmark on Friday, says he has only seen Bielsa’s softer side since breaking into the first-team at Elland Road.
“I haven’t seen him blow up,” Roberts said. “He was OK after Saturday (when Leeds lost 4-1 at West Brom).
“He always shakes everyone’s hand when we come in from the pitch. It’s always the same, win or lose. He was obviously not happy about Saturday, but that’s the same in every team after a result like that.”
Roberts joined Leeds from West Brom for £2.5m in January but injuries kept him out of the first-team picture until Bielsa’s arrival.
The 19-year-old, however, has made a big impact since with three goals in seven league starts.
Those goals have helped Leeds into third place in the Sky Bet Championship table and has coincided with Roberts making his mark on the international scene.
“I started as a winger with him (Bielsa),” said Roberts.
“But he’s seen me come away with Wales and play the No 9 role.
“He’s taught me a lot about runs in behind, staying up the pitch and making important movements.
“He’s opened my eyes to another part of my game that maybe I didn’t see as well before.
“He’s got so much respect in the game and everyone at Leeds has bought into that culture.”
Roberts’s breakthrough at Leeds has been replicated at international level under Wales boss Ryan Giggs.
He made his debut in September’s Nations League victory over Republic of Ireland and his first start against the same opponents last month, a 1-0 win in Dublin.
Wales will top the group and secure promotion to the top tier of the Nations League by beating Denmark in Cardiff.