Hi JTRI
There is no way of REALLY guaranteeing anything in life, yet many thread on these Forums (and in discussions about occupational health and safety in general) seek to find the magic bullet to do it.
So, you can have a system e.g. where you sit down with two roofers and go through the risk assessment, method statement or whatever it is might be called and then ask them to sign to say that they understand it.
But that doesn't mean they will do it when out of your sight!
You can also get them to complete a dynamic risk assessment on arrival and perhaps again, e.g. if the work continues to the next day. That may give you an idea of what they are thinking should be done OR what they think that you think they should be concluding if YOU had been there at the time.
All these bits of paper (or electronic equivalent) are good evidence but not conclusive and the only way to really know what is happening is to turn up preferably unannounced to see what ACTUALLY happens.
I got a very good lesson in the benefits on unannounced inspections when I was working in a food factory in the heatwave of Summer 1976.
Every third Thursday the auditor would turn up from the supermarket customer, so every third Thursday the windows would be shut, the wooden brushes would be hidden away and the shiny plastic ones would be brought out. Once the auditor had gone we could reopen the windows (thankfully) and get back to using the wooden brushes which were MUCH more effective when cleaning the floors.
There are many situations when unannounced inspections are simply impractical but this is rarely the case for roofwork, though there is always the risk that people high up will see you high end car from a distance! So, may be park it a distance away and walk up to site less easily to see. Sneaky, yes, but also entirely pragmatic!
When I worked for HSE there was a year that I found myself inspecting various sectors in the remote islands. One of my colleagues did construction on those islands and told us about the week when he couldn't find a single operational site - clearly the message had gone out. "Mr X is on the islands. Shut the site down and go and do all the other jobs you do." So, forearmed is forewarned. I would make my travel arrangements as late as possible and then reckon that I had up to 48 hours to do the most important visits on my schedule before the word would probably have spread that there's an HSE Inspector on the islands.
However it sounds as if you have the right sort of information to enable surveyors and you to make a good stab at the risk assessments. Perhaps ask the roofers how good a job THEY think you are doing?
As regards a dynamic risk assessment template, I don't have one, but most of the questions should be relatively obvious.
e.g. Is the access permanent or to be provided temporaily.
As example, I live in Scotland where rules were made in the 19th Century that any building with the lowest roof edge being 15 feet (4.5m) higher than surrounding ground had to be designed to incorporate permanent provision for access.
So, on a typical 4 storey tenement residential building this would usually be via either roof hatch or hatches with access via the roofspace and access to the roofspace either being from the top of the top of the communal stairway or through one or more ceilings in an individual flat OR one or more dormer windows to provide direct access to front and/or rear side of the roof.
But even if you know that it may not give the full picture. As example in the bulding I live in it's basement, three storeys + attic with a single dormer at the front of the attic giving access to a narrow flat roof. From there up two slopes to the ridge and two more slopes down to the rear gutter. Even a higher experienced slater wouldn't be able to see what the condition of the front and rear slopes is from ground level.
....and at risk of upsetting some on these Forums who like to take an absolutist position on preventing falls if your six teams are doing 20-30 jobs a week, then each team is doing an average of perhaps five jobs a week, some of which may be of very short duration where providing full height scaffolding front and rear is never going to meet the legal test of "reasonably practicability" (partly due to the risk to the scaffolders of erecting and striking the scaffolds).
You and your teams know what the range of jobs is, so you should be able to devise something appropriate to your and, more importantly, THEIR needs. Probably won't be perfect the first time but it can be tweaked as all understand the process better.
Good luck, Peter