Root, along with England colleagues Gary Ballance and Jonny Bairstow, will also be available for Yorkshire’s Royal London One-Day Cup quarter-final against Kent Spitfires in Canterbury on Thursday.
Sheffielder Root returns to the Yorkshire fold on the back of a good individual series for England against Pakistan, which saw him score 512 runs - including a double hundred at Old Trafford.
And the 25-year-old Sheffield Collegiate product said: “I always love coming back to the Yorkshire camp and playing in the big occasions.
“The lads have been red hot with the white ball in particular and I just want to help contribute to some huge wins for the club.
“The lads have been outstanding and no doubt there will be a huge contingent of supporters down at Edgbaston.
“We just have to go there and put on a show and make it a memorable day.”
Root played for Yorkshire in 2012 when they enjoyed their only other taste of T20 Finals Day. Yorkshire beat Sussex in the semi-final at Sophia Gardens, in Cardiff, but couldn’t get over the line against Hampshire despite South African David Miller’s unbeaten, 46-ball 72.
Bairstow added: “We haven’t done very well in the T20 competition in recent years. But seeing the quarter-final win over Glamorgan; it was very exciting, a very good crowd and a fantastic spectacle. For me it will be good just to feel part of it again and to get around the lads.”
Another player gearing up for a second Finals Day appearance is Azeem Rafiq, the skipper of Yorkshire League South side Sheffield and Phoenix United.
Rafiq, who also played in 2012, recently rejoined Yorkshire and was awarded his county cap at the weekend.
“I feel so honoured and proud,” the 25-year-old said.