Definitely build the soil as that's the key to most gardening, no matter what kind of plant. Please don't let them intimidate you. They are NOT that difficult. They will "tell you" what they want by how they grow. I'm sure you already know how to read other plants, and roses are the same. You just need to learn their language and "conjugation". As for "octopus arms", if a rose is advertised as making a decent climber, expect the arms. A rose which makes a "manageable shrub" in the British, or even Northern US climates, will generally explode when let loose in the warmer Southern California areas. Many roses will tend to be larger here than they are advertised over seas. I used to joke that McGredy floribundas were usually "suitable for pegging" as they often grew like Hybrid Perpetuals...octopus arms which provided many flowering laterals when trained like climbers. Quite a few British floribundas of the seventies and eighties performed similarly. You're fortunate to live in SoCal. Unless you're spending money on the once-flowering, old European Garden Roses, there are few roses you won't be happy with. Between not really receiving enough chill hours and getting far too many high heat hours which counter acts the chill hours, many of those types won't flower, actually grow backwards each year and/or never really perform as well as they do where they are better suited. Most others will probably give you an acceptable level of performance to make you happy.