Kinat Ad*nai Tzevaot says that there is a Great Rome and there is a Small Rome and there the Mashiachim (Sar HaPanim) sit, one in terms of Great Rome and one in terms of Small Rome and from there the sparks needed for Israel are sorted. And their suffering eases the punishment of Israel.
The Ramchal says (in Siman 36) that there are three states of holiness which fell downwards.... there are holy sparks which are the neshamot that are destined to emerge. There are holy sparks that belong to the spiritual luminaries themselves. There are holy sparks which sustain the sitra achra. All of these states need to be elevated and there are three functions at three appointed times which are needed to elevate them. The neshamot emerge first. When the process of their emergence is completed then the redemption will occur. The parts that belong to the spiritual luminaries will become manifest with the advent of Mashiach ben Yosef. If the generation is unworthy, then he will have to die and in death he will elevate them.