The Paris-born player, who represents the Ivory Coast, was carried off on a stretcher after falling backwards onto the pitch in the 18th minute with the game later abandoned at 1-1.
Ndicka was conscious but visibly in pain, rubbing his chest with his right hand as the medical team rushed towards him. Roma later said he was in "good spirits".
"First and second-level cardiological tests were administered that were negative for cardiac pathologies," Roma said in their latest statement.
"In light of the last tests undergone this morning, the medical situation is compatible with a thoracic trauma with minimal left pneumothorax."
Roma thanked the referee, fans at the Udine stadium and the hospital staff.
"In those frantic minutes of apprehension, we all together demonstrated sports values and placed protecting life in first place," Roma added.