The context emphasizes God's role in allowing many Jews to continue in their rejection of Christ (11:7–10). So the phrase their rejection likely refers to God’s rejection of Jews who do not believe.
their acceptance: This then refers to God’s acceptance of Jews into his kingdom. Paul uses similar language elsewhere to describe God’s welcoming action (see also 14:3 and 15:7).
The phrase life from the dead could describe the new spiritual life Jews receive when they turn to Christ (see 6:13). However, the wording more naturally points to the bodily resurrection of the dead. This resurrection will take place when Christ returns in glory (see, for example, 1 Thessalonians 4:13–18).