The win capped a disappointing season for the Wildcats (5-7, 2-6 Southeastern Conference) and kept Tennessee (5-7, 1-7) from reaching bowl eligibility with representatives from the Liberty Bowl on hand.
Kentucky's game plan was clear from the start to win for the first time in the series since 1984.
The Wildcats weren't going to be able to throw much with Roark, but instead tried to run misdirection plays and catch Tennessee off-guard while relying on their improving defense.
Roark led two scoring drives and Kentucky forced three turnovers, including a key one in a goal-line stand in the third quarter.
Roark had talked earlier in the week about needing to find a job after he graduated in May, but he left a strong impression in his final appearance at Commonwealth Stadium with injured quarterbacks Maxwell Smith (right shoulder) and Morgan Newton (right ankle, right shoulder) watching from the sideline.
Kentucky wore its black jerseys for the second time this season at the request of its 21 seniors and, on the first possession, Roark led Kentucky on a 15-play drive that lasted nearly eight minutes before it stalled at the Tennessee 7 and forced Craig McIntosh's 24-yard field goal. That would stay the only score until the fourth quarter, when Williams scored from the 6 to give Kentucky a 10-0 lead.
Tennessee had plenty of chances late, but committed three turnovers in the second half.
First, Ronnie Sneed intercepted Tyler Bray's pass at the Tennessee 34. But, with Kentucky seemingly stalled, it appeared to be only a matter of time before Tennessee's offense engaged. It happened when Bray found Rajion Neal behind cornerback Randall Burden for a 44-yard gain that set up first-and-goal on the 8.
But Neal failed to handle the snap out of a wildcat formation two plays later, and Collins Ukwu recovered the fumble for Kentucky before Roark restarted the offense.
First, he got linebacker A.J. Johnson to turn his back for a 24-yard gain into Tennessee territory. Roark made another key play a few minutes later, splitting the defense and breaking two tackles on a third-and-12 to gain 26 yards down to the Tennessee 7. Williams, who finished with 68 yards, scored two plays later on a 6-yard run that made it 10-0 with 14:12 left.
Tennessee struck right back when Bray found Neal on the post again against Burden for a 53-yard score that cut it to 10-7 with 12:52 left. Tennessee had three chances late, but Bray failed to move the offense beyond one first down and on fourth-and-17. Taiedo Smith intercepted Bray's pass to seal it.
Roark finished 4 of 6 for 15 yards passing.
Volunteers wide receiver Da'Rick Rogers caught two passes for 38 yards to boost his SEC-leading totals to 67 receptions for 1,040 yards, but Bray looked rusty in his second game back after missing five with a broken right thumb. He finished 15 of 38 for 215 yards.
The Vols last lost on the road to Kentucky in 1981 and, coupled with their 6-7 finish last year, have ended seasons with consecutive losing records for the first time since 1910-11.
They'll have a long offseason to think about this one by failing to topple a Wildcats team that had been in turmoil all week with rumors that coach Joker Phillips might not return for a third season.
Kentucky athletics director Mitch Barnhart said on the school's pregame show that nothing changed from when he publicly supported Phillips in October.
Phillips is 11-14 and 4-12 in SEC play over his first two seasons while the program won't go to a bowl for the first time in five years. Instead, the coach got a victory bath from a sideline water cooler all the same and fans rushed the field.