The three-day tour match at Grace Road concluded yesterday with England on 444-7 in response to the tourists’ 285.
Root’s magnificent knock follows innings of 236 and 182 for county side Yorkshire this season.
But limited-overs coach Giles, who took charge of the second string, has called for patience when assessing Root’s potential.
“We need to be guarded on how much we build the lad up, he’s only played a couple of Tests but so far so good,” said Giles.
“He works very hard and very specifically as well, and he’s worked his game out.”
Root has been named in England’s squad for this week’s first Test against New Zealand.
And, having scored 646 runs so far this season, hopes to become the first England player since 1988 to score 1,000 runs before June.