I have grown both 'Pergolèse' and 'Rose de Rescht', both on their own roots, for several decades. While the blossoms are quite similar--not lookalikes, but quite similar--and both bloom gratifyingly throughout the year, 'Pergolèse' sends out suckers and runners with some frequency, and 'Rose de Rescht' never does, absolutely never (I wish it would!). (Before anyone says, "But my 'Rose de Rescht' sends out suckers abundantly!", be aware that it appears that many who have what they think is 'Rose de Rescht' actually have the suckering 'Rose du Roi'.) Also, 'Pergolèse' is taller, branches less, and has a looser, more open, habit than the bushy 'Rose de Rescht'.