Shiny Swapping or SOS Chaining - Roar is not a problem
Roar won't work if the wild Pokemon is lower level that the Pokemon you have, I have had this happen with wild granbull in poni gauntlet when training.
If your still worried for some reason, then use a Pokemon with the ability soundproof like a kommo-o or something, but I'm almost certain that roar won't work as long as you are higher level.
SOS chaining takes a while to get going so you should probably multitask it or its going to get really boring. You need to get to a chain of 70 but once you get there then you are 4x as likely to find a shiny every growlithe called. You would also want a Pokemon with recycle and a leppa berry so you don't run out of PP and that same Pokemon with a healing move (a smeargle is very useful so if you don't mind setting one up then do that, moves would be recycle, healing move with 10PP, attacking move that can consistently kill growlithes, preferably with lots of PP, and the last move is false swipe to get growlithe to call for help more often) Also make sure you swap what growlithe is calling for help every so often so it doesnt struggle.
Shiny swapping takes alot less setup but each egg takes longer than it takes a growlithe to call for help so after you reach a 70 chain SOS is quicker. However shiny swapping is much faster when you start because every egg as an equal shiny chance. First you want a masuda method ditto so go look for one on gts if you dont have one already. You also want a magikarp and a growlithe. All you do is save the game, put magikarp and ditto in the nursery and then receive and hatch eggs, hoping you get a shiny karp. Every 50 or so eggs you might want to take the parents back, hatch your remaining eggs, and save and redo. This is because when you eventually get a shiny karp your gonna want to soft reset and replace the karp with growlithe in the nursery and start hatching growlithe eggs, so its quicker to get the shiny egg to be closer to when you last saved so you can go through less eggs to receive that egg.
Basically, lets say your super lucky and the shiny karp is the 10th egg. Well you want to soft reset and replace the parent to growlithe. The game basically knows what the Pokemon hatched from eggs will be like in terms of ivs, natures, gender, shininess, etc in advance. So that 10th egg will ALWAYS be shiny. I don't think your allowed to change both parents, so the ditto used must not leave the nursery when you swap karp with growlithe. The reason karp is used is because it hatches really fast.
Sources - Experience, Bulbapedia, and This shiny swap guide
