These are strictly ornamental. I would suggest L brackets on the structure itself and then you can install these over that.
OZCO doesn't have any control over this. You'd need to ask The Home Depot help desk.
The faux base plates are for decorative purposes only. You will need the 6x6 Post Base (item# 56608 or 51708 depending on the style) instead - and yes, it will support the beam to roof application you're referring to. Thank you! Let us know if you have more questions.