Unfortunately Warlord Games romans do not qualify at all! They depict troops from the early imperial period, while the Punic Wars require republican soldiers!
In 20mm there are certainly Zvezda figures! If they are anything like their napoleonic figures, they would be superb! And then there are Ceasar and Hät and others!!
For more info on 20mm-1/72(6) figures, you can consult this site
http://www.plasticsoldierreview.com/Periods.aspx It gives top info on all the sets currently on the market!
There are so many different troops involved on the Carthaginian side (mercenaries, celts, numidian cavalry, war elephants, etc) that I would strongly recommend you choose carefully the battle you want to show.
Hope that helps a little
Good luck with the project
Cheers
Romain