To add users users after a deployment to a Azure Analysis Services cube you can do this manually with the Management tools or with the Visual Studio. But with a Continiuos Deployment (CI/CD) and different stages, you need mostly add different users/groups to add to the roles. So, you need todo this dynamiccaly with some scipts. I found in the marketplace a addin to do this with DevOps by using a pipline. But, unfornatially this adding does not work and you can only onee user/group by using one step. So, I decided to do this with PowerShell to add more than one user in one step.
I added my deployment user as a SSAS admin with the portal (you can also do this with the Management Studio)

After that, I created this PowerShell script and added this to my Repo and published it to DevOps to use it inside a Pipeline: This script connects to my Analysis Service and adds a user to a role. use it inside a Pipeline: This script connects to my Analysis Service and adds a user to a role.

[CmdletBinding()]
param (
    $ParamUser,
    $ParamPassword
)

$myPassword = $ParamPassword
$myUsername = $ParamUser

$password = ConvertTo-SecureString $myPassword -AsPlainText -Force
$credential = New-Object System.Management.Automation.PSCredential ($myUsername, $password)
Login-AzAccount -Credential $credential
Import-Module SqlServer -DisableNameChecking

Add-RoleMember `
    -Server asazure://westus.asazure.windows.net/ssas001 `
    -membername "asadmin@plenz.onmicrosoft.com" `
    -database "adventureworks" `
    -rolename "Internet Sales Manager" `
    -Credential $credential

Here you see the script inside my Repo at DevOps

Next, I created a pipeline, and I added the needed credentials to connect to the SSAS server as variables.

After doing this, I created an Azure PowerShell task inside my pipeline this one uses the PowerShell script from the repo and pushes the variables as parameters to the script.

After tunning the pipeline, the user from the script is added to the role.