Elizabeth asked:

I am new to rose gardening. ... varying amounts of sun and
shade due to trees in other yards around us. We're in Ontario, zone
5.

Well, a couple of suggestions right off the bat. Roses need 5 to 6
hours of direct sunlight per day in order to do well, so don't do
anything (like planting trees that will interfere with your precious
sunlight). Next, pay very close attention to whether the variety of
rose you are considering is winter hardy. The Canadian government
sponsored a rose hybridizing program that produced roses that are
winter hardy to Zone 3 and 4. These are the series of roses called
the Canadian Exlorer roses and the Parkland roses. In zone 5 you have
a lot more varieites to work with besided these of course.

... What I
*want* over time is to have lots of greenery as a backdrop, and roses
as the main source of colour, with some perennials...

You can have climbing roses as a backdrop, if you have enough
sunlight.

If you want roses as a main source of color, make sure you get
varieites that rebloom regularly and in quantity. Floribundas and
modern Shrub roses fit this bill.

Clematis, Delphinium and Salvia make good rose companions.

I should add that on two sides of the yard, the back fence and one
side, there is ugly chain-link fence. .. So some taller plants would be
nice for privacy to cover the chain-link.

There are rose varieties that will grow tall and close for good cover,
but may I suggest that you install your own board fence on your side
of the chain link, or suggest to the neighbor that you would like
permission to remove the chain link fence in order to install a more
good looking fence. (A more expensive, but I think better option).

I'm thinking, bigger, green plants or small trees in the back of the
beds, then room for the roses, then perhaps something smaller ...

Climbing roses for the back shorter roses for the front. Low
perennials in front of that is my recommendation. I would avoid
planting any new trees unless you have a huge yard. Light. You need
light. Light is the key to great gardens. Another suggestion, is to
not just use flowers as borders. Putting a raised flower or rose bed
in the middle of a lawn is a great solution.

Have a good one,

Bob Bauer
http://www.rose-roses.com/