Dundee started well and Cammy Kerr and Max Anderson made some positive runs into the box. It paid off in 10 minutes when Anderson turned superbly into space on the corner of the penalty area and passed to Paul McGowan who set up Jordan Marshall to drill a low shot into the corner of the net from 18 yards.
Soon after McGowan had a good effort which on the wrong side of the post. Ryan Sweeney headed over after a good ball into the box. Perth saints came into the game and Lawlor had to make a fine save which he tipped the ball over the bar.
Second half and St Johnstone started well and Dundee looked to hit on the break, soon after Luke McCowan replaced Paul McMullen. Still saints pushed forward to try and level the game.
But they did level the game when Rooney headed home from six yards out after twice Dundee had cleared efforts off the line.
The Dark Blues made a double substitution, sending on Zak Rudden and Niall McGinn for Shaun Byrne and Paul McGowan. Dundee had the better of the last 15 minutes, doing most of the late attacking.
But no vital second goal for Dundee and St Johnstone looked happy to take the draw. Next up for Dundee is a trip to Aberdeen next Saturday.
Dundee: Lawlor, Kerr, Sweeney, McGhee, Marshall, Anderson (Mulligan 81), Byrne (Rudden 74), Adam (c), McMullan (McCowan 51), McGowan (McGinn 74), Mullen. Unused Subs: Sharp (gk), Fontaine, McDaid, Elliott, Ibsen Rossi.
Referee: Bobby Madden
Att: 7,937