Actually that's a Roman Chair in the picture.
They do have other equipment that are called Roman Chairs, primary for lower back and a leg combo device, but usually fall short of the original concept of a true Roman Chair. Probably the Roman Chair has been around for hundreds (that's 100's) of years in training history. Circus athletes and strongmen have used it as a training tool over the years.
The Roman Chair affects the quads very strongly and can also work the upper and lower abs extremely well. It even seems to strengthen the knees themselves. Though if having a recurring knee problem/injury, do take a bit of caution. As a leverage exercise, weight can be added, but generally it's used weight free. Easy at first, there is a different feel or stretch to the movement. DB's or a BB held as if doing a front squat.
Sissy squats will make a sissy out of the strongest squatter's in the gym...as the old saying goes. Sissy squats are a form of a superior quad stretching movement, which also affects the flexibility of the ankles and knees, when done the correct way. Most athlete's do a form of the Sissy squat in one way or another; track, football, baseball, etc.
The exercise requires practice to master the true form and effect of the movement. But it can be a rewarding effort. As with the Roman Chair, Sissy squats do not require adding weight. If you feel the need, than that's your choice. As with both exercises, higher reps offer the best results. 3x12-15 for example.
Good Luck.