All right. No offense, but your Bowser could use some work. Let's start with your approach. Bowser is not good at attacking from above. If you are above your opponent, your goal should be to get back to the ground rather than to engage them. Dair sucks - there is always a better option so try not to use it at all. Fair can be a good approach and I think it was the best approach I saw you use. SH flame is also good so long as you aren't too predictable with it. Fortress is never a good approach. Out of shield, it is lightning fast and does OK damage. As an approach, it is slow, low priority, not very damaging, and very punishable. I think I only saw you do this once, though. Also, Bowser's roll is pretty bad, so try to minimize rolling in general. The two bowsercides at the end only worked because, to be frank, your opponent sucked. Both were very avoidable and would not have been bowsercides anyways with any DI. The second one should have been especially easy to avoid because you were very obvious about it: on the last stock literally all you did was attempt bowsercides. Against a good player, that kind of stuf is going to get punished very hard. The suicide at the beginning could have been avoided if you DI'd into the edge, but you probably realize that.
Against ROB, you want to stay on his *** whenever you can because he outcamps and outprioritizes you. Keep in close and use your faster attacks. Again, this doesn't apply much to the ROB you faced because he was pretty bad. I don't have much experience with ROBs though, so if anyone has more experience fighting him, feel free to correct me.