Wednesday chairman Lee Strafford has demanded results quickly and the Sheffield side now face a must-win game at South Yorkshire neighbours Doncaster Rovers on Tuesday.
The Owls failed to make any impact in a scrappy opening period as Reading carved out the better chances.
Icelandic midfielder Gylfi Sigurdsson fired over from long range before lashing a free-kick inches wide of the target as Lee Grant scrambled across his goal-line.
Rasiak almost broke the deadlock in first-half stoppage time as he wriggled past two defenders but Grant dived bravely at his feet to block the six-yard shot.
The Poland international squandered another chance minutes after the re-start when he stretched to meet a Jobi McAnuff cross from the right but steered his header over the top from eight yards.
He was handed another opportunity as the Wednesday defence failed to close him down, finishing with a low strike scooped up by Grant, before Reading went ahead in the 49th minute.
McAnuff was again given too much space on the right flank as he picked out the lanky Rasiak who headed in from close range for his sixth of the season.
Full-back Tommy Spurr almost snatched an equaliser when he drilled in a fierce 25-yard strike, the ball spinning the wrong side of the far post with Adam Federici beaten, before striker Luke Varney hit the post with a spectacular overhead kick from Grant's long ball downfield.
Reading added a second in the 67th minute though with the simplest of goals. Dangerman McAnuff was again given time to drill in a low cross as Cisse side-footed past the helpless Grant from six yards.