However, the players' management say the pair had the correct clearance for the use of prescribed medication, including lodging therapeutic use exemptions (TUEs) with authorities.
Simon Porter, a player manager from the Essentially Group, which represent both players, said he has been aware of the bubbling story since the final in Spain on June 24.
"We have been aware of the issue for a few weeks. Our understanding and assurances we've had are all the documents around TUEs were in place."
Porter said Carter was receiving medication, probably cortisone, for a calf injury that ultimately forced him off the field for his Racing Metro Club in the Heineken Cup final against English club Saracens in May.
Paris-based L'Equipe newspaper, regarded as the bible of French sport, is claiming that France's official anti-doping agency conducted urine tests on all players involved in the final between Racing Metro and Toulon.
The tests were held at the Camp Nou facility, home of the famous Barcelona football club, on the eve of the final.
The surprise tests were conducted under a bilateral agreement between France and Spain.
L'Equipe reported "the first analytical results have detected abnormalities in the urine of three players of Racing".
Carter was man-of-the-match in Racing's 29-21 victory over Toulon while Rockocoko was also on the winning team on the wing and scored a brilliant chip-and-chase try in the first half. His fellow winger Juan Imhoff, a former Pumas international, also reportedly had anomalies in his urine tests.
The Toulon side featured former All Black Ma'a Nonu. Another All Black Chris Masoe turned out for Racing.
The French paper claimed the anomalies related to traces of "corticosteroids" which are different to steroids.
Corticosteriods are designed to help reduce inflammation.
L'Equipe is reporting that Carter, Rokocoko and Imhoff do not have a Therapeutic Use Exemption (TUE) which would have allowed to play even if they were taking the corticosteroids for medical purposes.
"These traces of steroids, prohibited substances in competition without permission," reported the paper.
However Porter said both players were relatively "relaxed" because they believed the club doctor had filled in the required documents.
Players' Association boss Rob Nichol said his organisation was aware of the issue but were also of the view that TUEs were in place.
Carter played 112 tests for the All Blacks. The victory clinched Racing's first Top 14 title since 1990.