The striker bagged a first-half goal as his side managed a draw despite playing most of the match with nine players.
Johannsson's side was down to nine men before the game was even 20 minutes old, as Nick Viergever saw red with 12 minutes gone before Nemanja Gudelj also received his marching orders in the 19th minute.
Despite the two-man deficit, AZ opened the scoring in the 25th minute, as Mattias Johansson put the home side ahead. After Roda equalized, Johannsson put his team in front again with a composed cut-back and finish into the far post in the 39th minute.
The home side was unable to hold on for all three points, however, as a late Vasil Skourtai goal meant the points were shared at the AFAS Stadion.
The U.S. international striker now has 10 goals in 12 Eredivisie games this campaign and 13 in 19 matches over all competitions.