I don't know if this falls under your category of rock opera, but Husker Du's Zen Arcade is an album that works marvelously as a unit. It's intended as an opera, but is not so blatant about it as, say, Tommy (which is also wonderful, but clearly lies in your realm of disqualification).

Others, as I quickly go through my collection:

Bob Mould - Workbook
Pearl Jam - Ten
Liz Phair - Exile in Guyville
The Pixies - Trompe le Monde
Psychedelic Furs - Book of Days (which is probably disqualified as well)
Sebadoh - Bakesale and harmacy
Sonic Youth - Daydream Nation (also maybe out, but phenomenal)
Soul Asylum - Made To Be Broken and Hang Time
Ultra Vivid Scene - Joy 1967-1990