An extra thousand pounds on a properly built roof is probably not a big deal. Think of how much weight there is when there is 6+ feet of snow for example, it's probably more. With solar you'll want a way to take the snow off so any weight that would be added by snow you'll be removing anyway.
Speaking of which I kind of came to the conclusion that my roof is just not steep enough for solar and the amount of work required to take snow off every morning is just not worth it for me. I did the shed as an experiment, and it was a constant battle especially because at one point we got freezing rain and it pretty much ruined them for most of the year. The snow/ice crust was just impossible to get off. I was producing around 10 watts most of winter.
This is my array, just 400w. Was hard finding panels but eventually found some on Amazon for a decent price. The bigger ones are super hard to find in Canada. Most sites don't actually show prices or have a buy option. The ones that do have a buy option want your virginity just to ship.
This is my shed array:
This is what they looked like most of the year, that snow is a crusty/icy type snow and does not come off:
They are finally clear now, but at this time of year we got lot of crappy wet/crusty type snow that really sticks but it does melt after a few days.
If I was to do this more serious like in an off grid setup, I would go with 3 large arrays (at least 10kw or so) of vertically mounted panels facing east, south and west. Key is to have them vertical so the freezing rain does not stick and it would also not require having to constantly go take snow off as normal snow would not stay on them. Worse case you might get driving freezing rain but hopefully it only affects one of the arrays and not all 3. We don't get lot of freezing rain here thankfully, but it only takes once to make an array inoperable for rest of the year. There's different things I could do to try to melt it off though, like a wood fired boiler system or nichrome wire or something. Nichrome wire is simplest but it would require a very large battery reserve.