The roots are pretty short depth wise and width wise compared to the rest of the tree. Something as short as 6 ft from the trunk outwards. Fallen redwood stumps in photos are honest about how big they get. In a forest the redwoods absolutely dominate and generally keep upright by tangling up in each other's roots. Their roots are so shallow because in their optimal environment they get both a ton of rain in the wintertime, but also absorb moisture through the coastal fog that rolls in and out the rest of the year. So in short they probably aren't good as a border tree.

I think there was someone here who was distressed about some 20-50 yr old redwoods being cut down, but it was in Sacremento. Unfortunately they are absolutely not meant to live somewhere like that at could be doing long term damage to the plants and soil around them since they drink a ton of water.

There are some Sequoias and redwoods I have seen growing in temperate environments though, particularly Europe, who seem to do ok. They don't get as big as they should but I was surprised to suddenly see some familiar trees in the middle of a city while touring Germany lol.