Roderick/Editions
This is a partial list that doesn't include translations. For more details, see ISFDB.
Sladek originally planned Roderick as a single novel in three sections. The first two sections were published separately in 1980 as Roderick, or the Education of a Young Machine; the final section appeared in 1983 as Roderick at Random, or Further Education of a Young Machine. The entire work was finally reissued together in 2001, after Sladek's death, as The Complete Roderick. All the notes on the rest of this site refer to the 2001 Gollancz edition.
US
Part 1 (Roderick)
Carroll & Graf, 1987. Paperback. Reprint of the 1980 UK edition. Cover art (by Daniel R. Horne): robot in a baseball cap with a six-pack of what looks like Pepsi. ISBN 0881843253
Timescape/Pocket Books, 1982. Paperback. Cover art (by Carl Lundgren): indescribably unpleasant painting of a young kid (Chauncey?) punching a chunky robot while another kid looks on from inside a garbage can. Caption: "the lusty, rusty adventures of a boy of steel in a world of men!" According to ISFDB, this edition is missing some of the text, but I don't know what part. So there are several reasons to avoid it. ISBN 0671448862
Part 2 (Roderick at Random)
Carroll & Graf, 1988. Paperback. Cover art (by Daniel R. Horne): the same rural-looking robot from the Carroll & Graf Roderick, same Pepsi cans, this time with overalls and a pitchfork. ISBN 0881843415
UK & Australia
Combined (The Complete Roderick)
Overlook SF&F Classics, 2004. Trade paperback. Cover art (artist unknown): two blank mannequin heads with bar codes. ISBN 1585675873
Gollancz SF Masterworks, 2001. Trade paperback. Cover art (by Chris Moore): shiny robot welding something. ISBN 1857983408
Part 1 (Roderick)
Granada, 1982. Paperback. Cover art (by Ray Winder): "Creation of Adam" homage, human/divine hand touching robot hand. ISBN 0586045392
Granada, 1980. Hardcover. No cover art. ISBN 0246114371
Part 2 (Roderick at Random)
Kerosina Books, 1990. Hardcover. Cover art: same as the Granada edition. ISBN 0948893427
Granada, 1983. Paperback. Cover art (by Tim White): "ascent of man"-style series of increasingly humanoid robots walking in a line. ISBN 0586052313