no there's nothing senjutsu about the rasengan, all it is, is your own chakra spinning really fast in a ball i.e. training with water balloon, rubber ball, balloon. rasengan is just naruto's only offensive move. when jiraya became a sage with the 2 elder toads, he attacked the pains with everything but a rasengan.
they just keep on adding senjutsu users every year!
first it was jiraya, ok sure, then of course the elder toads
then of course naruto learns it
then we find out kabuto learned it from the snakes, ok makes sense, and then that orichimaru couldn't master it but developed the cursed seal with it and juhgo's ppl.
ok still makes sense.
then all of a sudden the first is using it, cuz... he's the first he just knows it.
now all of a sudden minato knows senjutsu, when it took him 3 years to master and create the rasengan (where did he find the time to master senjutsu) not only that, but it looks like he has perfect senjutsu (like naruto), when jiraya turns into an ugly toad man.