If Satan is not omnipresent and supposedly wanders around like a roaring lion, how can he tempt and interact with all humans? There are millions of human beings and there is no way that Satan can interact/tempt all of us in a one-on-one relationship. So how does Satan perform his evil works?  I know that I am a sinner and have sin inherently in me but I don't see how Satan personally has had anything to do with me sinning.  It all seems to stem from my own evil nature. Thoughts?
Satan is most assuredly not omnipresent, Satan was and is an Angel (although he be a fallen Angel) and you must remember two things.


Satan (Lucifer) has no more power or ability than any of the other Angels.
When Lucifer was ejected from Heaven one third of the Angels were ejected with him:


Revelation 12:9  KJV 


  And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him. 


Rev 12:4 KJV


  Now the dragon’s tail swept away a third of the stars in heaven and hurled them to the earth. Then the dragon stood before the woman who was about to give birth, so that he might devour her child as soon as it was born.


These fallen angels are also Devils

Luke 8:30 KJV


  And Jesus asked him, saying, What is thy name? And he said, Legion: because many devils were entered into him. 


Some of these devils assist Satan in his efforts to tempt man away from God. The reason that they are so successful in their efforts to tempt us is because Satan has disguised Sin as a pleasant and desirable thing to have, and unfortunately having the knowledge of good and evil did nothing for our ability to see sin in its true character. Illicit sex would surely not be as tempting if it was seen ahead of time that it can lead to AIDS, or the many other STD's.

For some reason Satan has been able to disguise sin so completely that man will fall into his traps over and over.

Just consider the undesirable effects caused by not observing the 10 commandments.

It appears that man has been just as blinded to true beauty as when God destroyed the World in Noah's time.

Genesis 6:5  KJV 


  And GOD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.