VERB (3)

1. make a rolling motion or turn;
- Example: "The dog rolled over"

2. negociate to repay a loan at a later date for an additional fee;
- Example: "roll over a loan"

3. re-invest (a previous investment) into a similar fund or security;
- Example: "She rolled over her IRA"

WordNet (r) 3.0 (2006):

roll over
    v 1: make a rolling motion or turn; "The dog rolled over"
    2: negociate to repay a loan at a later date for an additional
       fee; "roll over a loan"
    3: re-invest (a previous investment) into a similar fund or
       security; "She rolled over her IRA"