All 'advanced' skills are just a combination of the basics. Learn and master the building blocks and you can combine them to work on these skills.
I am not a professional acrobat or gymnast, and my form is still decidedly rough, but I can put together what I know to perform the skills you see here.
Forward roll - (Pull-up strength + False grip strength + Handstand pressing/Ring dip strength + Abdominal compression strength)
Stalder press - (Handstand balance + Handstand press/Planche work + Lower body mobility)
Backward roll - (Pull-up strength + False grip strength + Abdominal compression strength + Ring dip strength)
One arm elbow lever to handstand - (Handstand balance + One arm elbow lever balance + Handstand pushup strength)
Break down a skill into its components, then attack your weaknesses.