Jackryan - for your roku3 and chromecast to work here, you'll need a US based IP, but you need to change your DNS on your router as well.
Go to unotelly.com and sign up for a free 1 week trial, once you sign up, look for the insrtructions on how to change your DNS on your router in their FAQ. Most branded routers are there already with instructions on how to change your DNS, if you're not familiar with your router.
After that, connect your Roku wired or wirelessly to your router and you should be able to add the subscription based US channels like netflix, hulu, etc.
If you've already connected your roku to the internet, it will already have a Philippines-based IP so even if you use the above steps, it won't work. You'll need to reset to factory settings first, then do the steps I mentioned above.
To factory reset your roku, simply go to settings and at the bottom of the list is factory reset. Before you do your factory reset, make sure your roku is not connected to your network. Hope that helps, let me know if you need anything else.