Retirement Account Portability Act of 2003 - Amends the Internal Revenue Code and the Employee Retirement Income Security Act of 1974 with respect to pensions and retirement assets to: (1) permit nonspouse beneficiaries (children, parents, etc.) to rollover retirement plan distributions; (2) revise provisions concerning the determination of exercise of control by a beneficiary or participant upon certain rollovers and distributions; (3) provide for the faster vesting of employer nonelective contributions; (4) eliminate the higher (25 percent versus 10 percent) penalty on certain early "simple retirement account" (SIMPLE) distributions; (5) remove specified restrictions on SIMPLE plan portability; (6) revise provisions concerning state and local government pension programs; (7) permit direct rollovers from retirement plans to Roth IRAs; and (8) allow certain mandatory distributions under $5,000 to be made to the Pension Benefit Guarantee Corporation.