Graham Onions' second five-wicket haul of the season has put Durham in command of their LV= County Championship Division One match against Middlesex at Chester-le-Street.
It could have been much worse for the visitors, who recovered from 35-5 to make 196 before Durham stretched their lead to 100 by reaching 37-0 in their second innings.
Middlesex resumed on 11-2 and that became four inside the first hour's play when Joe Denly was caught at second slip by Scott Borthwick and left-hander Dawid Malan fell lbw, Onions taking both wickets.
The resumption after lunch was delayed before, in the third over, Ben Stokes hit nightwatchman Tom Smith on the boot to gain an lbw verdict.
Onions had to be recalled and there was an element of fortune about the breakthrough as John Simpson toe-ended a short ball to mid-off to depart for 42, made off 51 balls with eight fours.
Paul Collingwood then clung on at the second attempt to an edge from Gareth Berg to give Onions 5-26 at the time.
Those figures were slightly spoilt by Dexter taking three fours off an over and he reached his 98-ball half-century by cover-driving Stokes for his ninth four.
But Stokes nipped one back to find an inside edge and have Dexter caught behind on 52 before Harris showed his batting prowess by making 37.
He finally hit a full toss from Scott Borthwick to mid-wicket and without addition Roland-Jones chipped Mark Wood to mid-on.
Durham had what looked likely to be a tricky 11 overs to bat in gloomy conditions, but Middlesex bowled too short to Mark Stoneman, who cut and pulled his way to 31, with Keaton Jennings surviving on six.