Furthermore by making salvation conditioned upon believing the gospel, God had made salvation contingent not only upon hearing the message, but upon Christians disseminating the message. For Paul continues in Rom 10:15 saying, "And how can they preach unless they are sent?" If people don't hear the message they cannot be saved. And thus if no one is sent to tell them the message, they cannot be saved. Which is why Paul was so upset at the opposition he faced. "For you, brothers, became imitators of God’s churches in Judea, which are in Christ Jesus: You suffered from your own countrymen the same things those churches suffered from the Jews, who killed the Lord Jesus and the prophets and also drove us out. They displease God and are hostile to all men in their effort to keep us from speaking to the Gentiles so that they may be saved. In this way they always heap up their sins to the limit. The wrath of God has come upon them at last." 1Thess 2:14-16 Far from being the hyper-Calvinist who would say to the missionary, "If God wants to save those foreigners he can do it without your help!", God has made salvation dependent upon those who disseminate the gospel. God didn't have to make it that way, but in His sovereignty He did! And I believe God did so that we believers may fellowship with Christ in saving people. "We are therefore Christ’s ambassadors, as though God were making his appeal through us. We implore you on Christ’s behalf: Be reconciled to God." 2Cor 5:20 And those unbelievers opposing the dissemination of the message will receive even greater judgement against themselves.
If you are a believer but are not involved in disseminating the message of the gospel, there may end up many spending eternity in hell who could have been saved had you but lifted a finger. And I say that quite literally as given the internet, the dissemination of the message may require of you no more than pushing a few buttons on a keyboard. So what's your excuse?
"I am not ashamed of the gospel, because it is the power of God for the salvation of everyone who believes: first for the Jew, then for the Gentile. For in the gospel a righteousness from God is revealed, a righteousness that is by faith" Rom 1:16-17a
"Finally, brothers, pray for us that the message of the Lord may spread rapidly and be honored, just as it was with you." 2Th 3:1