Can't help you with rentals at all, but as far as roads to ride are you looking for canyons or scenery? Either way most decent roads are about an hour ride away but here is a few options I frequently do.
Ortega Hwy - closest canyon to orange county, very easy sweeping turns but can get pretty bad traffic later in the day.
Rim of the world - CA 18 to the 330, gorgeous scenic road up in the mountains by lake arrowhead, fairly easy as well as long as there is no ice up there, about an hour inland
Julian, CA - CA 79, 76, 78, you can take any of these roads in. 79 is the most scenic is longer but the most scenic. Its a cool little town that is all about apples (pies, cider, etc) can get pretty busy on weekends. About two hours south.
Palomar Mtn Road - off of the CA 76. My favorite of the bunch, short 10 mile extremely technical road with 4000 ft of elevation. If you like twisty roads this is a must IMO. About an hour and a half south.
Idyllwild - CA 243, 74. Good intermediate twistys out in the middle of nowhere, semi popular with other riders. about an hour inland.
Mullholland Hwy - probably one of the more famous roads that can be a fun hangout on freeways, cool to see once but there is only about 2 miles of decent twisty area's and traffic is terrible on weekends. about an hour north (with no traffic)
Angeles Crest Hwy/Los Angeles forest - probably the best canyons in LA, unfortunately ACH is closed through wrightwood so don't expect to ride all the way through currently, still there is over 30 miles of twisty roads open, about an hour north