No, he wouldn't have to be put on the 40 man roster if he was taken in the AAA or AA protions of the rule 5 draft.
---------------------------------------------------------------
There are three separate phases in the Rule 5 Draft: the Major League phase, the Class AAA phase and the Class AA phase. A player selected in one of the three phases must be placed at the same level of the phase in which the player was selected. Within each phase, only eligible players from a lower classification club are eligible for selection. For example, in the AAA phase, players must be selected from a club's AA or lower roster and must be placed on the selecting club's AAA roster."
If a player is released and then re-signed by the same club within a year, the player becomes eligible for the next Rule 5 Draft. A Major League Club may designate any player on one of its Minor League rosters to be subject to selection who otherwise would not be eligible.
The selecting club must pay the club from which a player is selected:
(1) $50,000, if the selected player is placed on a Major League roster;
(2) $12,000, if the selected player is placed on a Class AAA roster;
(3) $4,000, if the selected player is placed on a Class AA roster.
A player drafted to a Major League level must remain at that club for the duration of the season unless offered back to the team from which he was selected. Players drafted to a AAA or AA club should be offered an opportunity to remain at that level during spring training, but it is not required.
------------------------------------------------------
http://www.whitecaps-baseball.com/ABOUT/faqs.html
Hope this helps.
Just as an FYI, often you'll see players from A ball promoted to the AA or AAA level if the team wants to add some protection to keep a player right before the rule 5 draft. One reason is that the higher the level, the more it costs to select the player. Another is because of the spirit of the law where a player has to be "offered and opportunity to remain at that level". Can't say I've ever heard of a player returned though by a team who violated the "spirit of the rule".
Edit: As far as Randolph goes, here's how the options work:
"When a player is added to a 40-man roster for the first time, the major league team is permitted three optional assignments of his contract, or three "option years." This gives them the option to assign that player to the minor leagues without requiring him to clear waivers. For each season thereafter in which the player is assigned to a minor league team, one option is used up."
Randolph has never pitched at the major league level. In 1999 he pitched for the DBacks rookie team here in Tucson, then AA, and AAA. Now I don't know if he's been on the 40 man roster for the last 3 years or more, but that could explain why he's out of options. Although it isn't clear, I think that once a player is on the 40 man roster, his options clock starts and it's 3 years whether he goes up to the major league club or not. Could be wrong on that, but it's my guess.