What did the Romans take from Britain after the invasion?

It is an open question whether, in fact, "Rome" ever really withdrew from England.

While the military garrison, or members of it, may have returned to Rome, many of the Romans of the English garrison would have created families among the English, married English women and had children, so they wouldn't have been returning to Rome. Even those who may have had wives and children in Rome would have made lives and families among the English. Such alliances were not unusual in those days when life was short and brutal.

As far as what the returning Romans would have taken with them, if they had personal possessions such as clothing, weapons, jewelry, or personal items they would have taken them if they could carry them on foot all the way back to Rome, but it's doubtful that they took much except the small amount of food ("bread") that they could carry to the next place where they would find more food in order to continue their long journey. If they had a horse or horses, they would have taken it or them. But members of the Roman legions, who traveled on foot and had to carry their weapons and military equipment, because they might have to fight on the way back to Rome, so extraneous burdens that might mean less ability to fight successfully would have been left behind. As they moved along the roads back to Rome they would have found food and water and would have bought or stolen whatever they needed, as did everyone else in those times.