The captain missed the agonising one-run defeat against Yorkshire at Headingley at the weekend due to a finger ligament injury picked up in the recnt win over Glamorgan.
Rossington will undergo a fitness test at the County Ground on Wednesday, with head coach David Ripley prepared to let the 27-year-old make the final decision on whether he is ready for four full days of cricket.
"Adam is having a fitness test this morning, so we will see how that goes," said Ripley ahead of Northants' training session at Wantage Road.
"He had a little bat yesterday, and gently caught a few balls, so we will have to crank it up today and see where he is.
"We have a week off next week, but if he is fit Adam is our captain and we want him back if he is able to play.
"If Adam says he is fit then I have no hesitation in sticking him in.
"If he is catching balls as he normally does, and he is pain free, then I think there is a good chance he will play.
"But if he is catching balls as he normally would and he is in pain, then I think we will utilise that extra week off and have him fully fit by the time we play Lancashire.
"But Adam will lead that, he is our captain, he wants to get back on the field, and if he thinks he can then we will back that up."
Ricardo Vasconcelos stepped in behind the stumps against Yorkshire, and also as captain, and the 23-year-old is primed to do the same if Rossington doesn't make it this week.
There are no other injury concerns for Ripley ahead of the visit of Sussex, and the 13-man squad is likely to be very similar to the one that travelled to Leeds.
Sussex are currently third in the Group 3 table, just four points ahead of fourth-placed Northants, and they may yet include England fast bowler Jofra Archer in their line-up.
Archer made his comeback from elbow and hand injuries this week, and is currently playing for Sussex IIs in their match with Surrey.
He batted on Tuesday, making 35 from 46 balls as Sussex made 287 for six, and is due to bowl today (Wednesday).