There was a wicket in the second over of the day to get Middlesex going as makeshift opener George Balderson was undone by a Higgins delivery that nipped back to have him lbw for eight.
Jennings and Josh Bohannon then combined to put on 56 – in what turned out to be the highest partnership of the innings – although the bowling remained tight.
But Higgins returned for his second spell and struck with his first ball as Bohannon tickled it behind for 20.
There was then a big third wicket before lunch as Australia batter Marcus Harris (five) was deceived by a ball outside off-stump and scooped it to mid-on where Naavya Sharma took a good, low diving catch to leave the hosts 74-3.
Only four more runs were added before lunch and after the interval, Jennings brought up his third half-century in five innings off 107 balls as Lancashire looked to rebuild.
But Michael Jones was cleaned up by a lovely delivery from teenager Morgan to make it 115-4 to go for 27 and that became 128-5 as a frantic innings from Matty Hurst (seven) ended with him offering a simple catch to fourth slip off Sharma.
Green joined Jennings at the crease and while the overseas player was dropped on 13, Middlesex claimed the prize scalp when Roland-Jones produced a fine ball that Jennings nicked behind to leave the hosts in trouble at 151-6.
While only 13 runs later, Tom Hartley was caught behind for three to give Higgins his third wicket.
Bad light produced an early tea before the last rites of Lancashire’s innings were played out as Tom Bailey fell for 11, Mitch Stanley was clean bowled by Roland-Jones for one and Green was last man to fall, bowled by Morgan as the 18-year-old finished with fine figures of 3-41.