The defending champions had looked to be on their way to defeat when defender Henk Dijkhuizen put Roda in front after 34 minutes.
But substitute Riedewald saved the day for Frank de Boer's men, the defender becoming the youngest player to score on debut in the Eredivisie as he equalised two minutes from time.
That was not the end of the drama, though, Riedewald netting again with the winner in the second minute of injury time as Ajax leapfrogged Vitesse into pole position.
PSV earned their second straight win by cruising to a comfortable 2-0 win over struggling 10-man ADO Den Haag.
Striker Jurgen Locadia gave the hosts the lead from the penalty spot after goalkeeper Gino Coutinho was sent off for a foul on Memphis Depay.
And Locadia made sure of the points eight minutes later with a close-range finish, although the visitors did waste a chance to score a late consolation as Tom Beugelsdijk's penalty was saved by Jeroen Zoet.
Groningen stay sixth following their emphatic 5-2 victory against bottom club NEC.
Goals from Michael de Leeuw and Filip Kostic put Groningen in command, before victory was all but confirmed thanks to a Rens van Eijden own goal and a second from De Leeuw.
NEC did pull goals back through Christoph Hemlein and Alireza Jahanbakhsh, but De Leeuw completed his hat-trick midway through the second half to round off a fine win.
Elsewhere, Go Ahead Eagles overcame Utrecht 2-1 in a mid-table clash.
