In SR, there is a simple, frame independent way to look at this. In SR, there is the notion of invariant mass. The invariant mass of the rocket never changes, no matter what its velocity relative to the solar system is. Similarly, the invariant mass of the solar system as a whole never changes, no matter what the relative velocity of rocket and sun are.
However, there is a nuance here. The invariant mass of the system of solar system plus rocket can be made arbitrarily large as their relative velocity increases arbitrarily close to c (speaking of SR only). Note that this is a 'mass' of the system as a whole, not attributable to the rocket or the solar system. Note also, that this 'system invariant mass' is unchanged (in SR) whether the rocket is far away from the solar system or inside it. But the 'invariant energy density' peaks when the rocket is inside the solar system. But ...
to discuss gravity, we need GR rather than SR. There is no simple analog of invariant mass in GR. However, if one assumes an empty universe with no dark energy, just the solar system and rocket, there are GR arguments that suggest as the rocket and solar system approach each other, they can collapse into a BH. This would be a collective interaction, not attributable to any component, and it would involve the whole system - there would be one large BH formed. The relevant notion in GR is the 'hoop conjecture'.