Striker Dan Gifford, pictured, and defender Harvey Hughes have joined up with the Nyewood Lane outfit ahead of the Isthmian premier division home showdown against rivals Worthing on December 27 and the busy schedule thereafter.
Highly-rated Gifford, 18, is a goal-getter who has already scored eight in 11 this season for Pompey's academy side, and has been on the bench for the first team.
Full-back Hughes,18, made his first-team debut for the Blues, appearing in the 3-0 home win over Crystal Palace U21 in the Papa John's EFL Trophy.
Both players are likely to feature for Portsmouth against Exeter City in the same competition in January, but it is anticipated that they will be able to return to the Rocks following that match.
Rocks general manager Simon Cook said: "As usual, we are extremely grateful to Portsmouth and hope that both Dan and Harvey benefit from their time with us."