need advice

Firstly, that seems like a perfectly good reason to have the early years practitioner replaced. You have to have confidence in those who are to support yourself and your son.

Now to the roaring. This is quite a difficult issue, that heavily impacts your family life. But while it looks like a very aggressive behavour it is in fact testament to his good nature: when driven to the edges of his evolope of tolerance he still chooses to express himself verbally; many others strike. Whereas he is to be congratulted for every instance in which he endures intolerable stress (and he certainly is even if it is currently unknown what the stressors are) without recourse to violence, he certainly needs help if he is to avoid a great deal of social exclusion.

First, after he has had a "meltdown" when he is calm but not so long after that he has forgotton the incident, pleasantly seek to establish what angered or hurt him. If you know his triggers you can try to eliminate them. Consider sound and smell as senses he might experience overloading. Cooking noise/odor, electrical hum, doorbells and phones...many things might be affecting his sensorium in ways you wouldnt expect. Log what is occuring when a "meltdown" occurs and look for patterns.

Second, can you help him express anger/frustration/pain more verbally than a roar. Perhaps you could teach him some milder expleetives so he has tools to express himself in ways that make more sense to those around him. I know teaching a child to swear seems extreem but he is likely to encounter these terms soon enough and they may prove a gateway to more effective self-expression.

Third, and this is where you and your son can really make progress in moderating his behavour: work with him to identify the internal process that culminates with being unable to cope with a stressful situation. If he can see the anger/pain rising then he can take steps to relieve himself before the situation becomes critical.

Fourth and Lastly, and without criticism, if you can get better at spoting the rage coming then you can help him remove himself from the situation as in option 3. It is not unlikely that he roars out of frustration that his previous signals of distress prove ineffective in requesting support from those around him.The practitioner really should be working on this stuff, get a new one and talk to that one about getting daily support as it is likely to be necessary to have two people availiable at all times so one can comfort the roaring child and one the sister. 

Pls bear in mind that 3+4 may prove dificult or impossible as the pain/rage may arise very strongly and suddenly, but it needs trying and 1+2 can and will help, take heart.

As an aside: what a berserker he would have made if society still valued such!

Firstly, that seems like a perfectly good reason to have the early years practitioner replaced. You have to have confidence in those who are to support yourself and your son.

Now to the roaring. This is quite a difficult issue, that heavily impacts your family life. But while it looks like a very aggressive behavour it is in fact testament to his good nature: when driven to the edges of his evolope of tolerance he still chooses to express himself verbally; many others strike. Whereas he is to be congratulted for every instance in which he endures intolerable stress (and he certainly is even if it is currently unknown what the stressors are) without recourse to violence, he certainly needs help if he is to avoid a great deal of social exclusion.

First, after he has had a "meltdown" when he is calm but not so long after that he has forgotton the incident, pleasantly seek to establish what angered or hurt him. If you know his triggers you can try to eliminate them. Consider sound and smell as senses he might experience overloading. Cooking noise/odor, electrical hum, doorbells and phones...many things might be affecting his sensorium in ways you wouldnt expect. Log what is occuring when a "meltdown" occurs and look for patterns.

Second, can you help him express anger/frustration/pain more verbally than a roar. Perhaps you could teach him some milder expleetives so he has tools to express himself in ways that make more sense to those around him. I know teaching a child to swear seems extreem but he is likely to encounter these terms soon enough and they may prove a gateway to more effective self-expression.

Third, and this is where you and your son can really make progress in moderating his behavour: work with him to identify the internal process that culminates with being unable to cope with a stressful situation. If he can see the anger/pain rising then he can take steps to relieve himself before the situation becomes critical.

Fourth and Lastly, and without criticism, if you can get better at spoting the rage coming then you can help him remove himself from the situation as in option 3. It is not unlikely that he roars out of frustration that his previous signals of distress prove ineffective in requesting support from those around him.The practitioner really should be working on this stuff, get a new one and talk to that one about getting daily support as it is likely to be necessary to have two people availiable at all times so one can comfort the roaring child and one the sister. 

Pls bear in mind that 3+4 may prove dificult or impossible as the pain/rage may arise very strongly and suddenly, but it needs trying and 1+2 can and will help, take heart.

As an aside: what a berserker he would have made if society still valued such!