The pit is symbolic of something. Him roaming the earth is symbolic of something. Futurists make the mistake of approaching Revelation as a future-timetable when it's a series of theological images preaching the gospel to suffering Christians. It describes, roughly, what life will be like between Jesus Resurrection and his Return. There will be the temptations of both persecution and prosperity. Watch out!
The "Millennium" isn't a literal amount of time. Instead John is using the common Hebrew number symbolism of a very long time. The use of 1000 in the Hebrew is often like the use of 'a gazillion' in English. It just means a lot, or the complete number of. EG: Psalm 50 the “Cattle on 1000 hills” - what about the other million hills on earth?
EG: Deuteronomy 1:11 - is God only going to increase Israel 1000 fold? Only? What about the “New Israel” - us - the church? Limited to a thousandfold increase from their numbers back then?
EG: Psalm 91:7 - is it 1000 or 10,000 - the verse uses these interchangeably?
EG: Deuteronomy 7:9 - is God only faithful for 1000 generations and then becomes unfaithful on the 1001st generation?
EG: Psalm 105:8 - is it 1000 generations or forever?
EG: Psalms 84:10 - Is one day with God’s people better than 1000 literal days or 2.7 years, or is this a qualitative assessment of where it is better to DWELL for a long time?
The number 1000 is either a picture of forever - or a great many number. I’m an Amil in that I believe that Revelation 20 teaches us there will be a great number of years between the Lord’s resurrection and his return. We’ve been in these '1000 years' for 2000 years and counting.
But what are we to make of Satan and this pit?
Surely he’s alive and active now? That’s a good question - but it helps us understand Revelation better. Rev 13 is a picture of Satan inspiring the Roman government persecution against God’s people. It's a warning that this will not only happen under the Romans, but creeps up throughout history. But the picture of the safety of God’s people in the next chapter should also comfort Christians who went through Hitler’s Holocaust, or Soviet oppression, or even Chinese or North Korean oppression today. So Satan is very much alive and active today.
But he is ALSO bound - at exactly the same time. How does this work? We’ve got to understand the imagery is not a geographic reality - Satan being bound in a literal pit - but a theological statement. Satan is bound with regard to 'deceiving the nations' as the gospel goes forward. That shows how ineffectual he is to prevent the growth of God's kingdom. There are now roughly a million Christians in IRAN - where there is intense persecution of Christians. As God's gospel charges into new lands, Satan's ability to 'deceive the nations' is in retreat. The article below summarises this for us:-
In my mind, though I tend to believe the pit might be literal, I'm not insisting that that is the only option, the point being as follows, assuming the pit might not be literal. Revelation 20 depicts satan chained, then cast into, then locked up, in a pit. Therefore, it is not reasonable if when he is depicted like that that he is also depicted persecuting the woman that brought forth Jesus, for example. That he is depicted walking about freely, as a roaring lion, seeking whom he might devour. That is not compatible with imagery involving someone that is depicted bound in a pit.
If the Bible is using real world imagery, the imagery has to make logical sense. In the real world if a lion was trapped in a pit, this same lion would not also be walking about freely outside of the pit at the same time. The lion would have to be omnipresent in order to do something like that. Clearly, only God has omnipresent abilities, lions certainly don't, nor does satan.
Even if one argues that when satan is in the pit it is only to prevent him from deceiving the nations, that this has zero to do with him walking about freely, as a roaring lion, seeking whom he might devour---so what? The imagery simply isn't compatible because only someone with omnipresent abilities could be physically in more than one place at a time. Clearly, being chained up, cast into a pit, then locked up in does not remotely fit imagery depicting this same one walking about freely outside of the pit at the same time. That paints an illogical picture, that satan, who is not God, that he is also omnipresent like God is because he can be in the pit locked away and at the same time, this same satan can also be walking about freely outside of the pit.
Job 1:6 Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them.
7 And the LORD said unto Satan, Whence comest thou? Then Satan answered the LORD, and said, From going to and fro in the earth, and from walking up and down in it.
8 And the LORD said unto Satan, Hast thou considered my servant Job, that there is none like him in the earth, a perfect and an upright man, one that feareth God, and escheweth evil?
9 Then Satan answered the LORD, and said, Doth Job fear God for nought?
Take this account, for example. Imagine while satan is standing there talking to God like that, that this same satan is also still going to and fro in the earth, and walking up and down in it, at the same time. Totally preposterous of course, since satan would have to have omnipresent abilities in order to do that. In the same way then, imagine when satan is depicted locked up in the pit, he is also walking about freely outside of the pit at the same time. There is no logic to it.