Rosparam load without overriding

edit

I ran into the same issue and ended up creating this script:

#!/bin/bash
# $0 is the script name, $1 id the first ARG, $2 is second...

if [ "$2" = "" ]
then
  echo "Usage: $0 <filename> <namespace>"
else
  dump_command="rosparam dump"
  load_command="rosparam load"

  FILE="$1"  
  NAMESPACE="$2"
  IS_NAMESPACE=$(rosparam list | /bin/egrep "$NAMESPACE")

  if [ -z "$IS_NAMESPACE" ];
  then
    echo "No previous Namespace found, simply loading new parameters"
    command="$load_command $FILE $NAMESPACE"
    eval $command
  else           

    #Dumps the current parameters in the server
    command="$dump_command dump_tmp.txt $NAMESPACE"
    eval $command

    #Temporarly loads the new parameters
    command="$load_command $FILE $NAMESPACE"
    eval $command

    #Dumps the new parameters
    command="$dump_command load_tmp.txt $NAMESPACE"
    eval $command

    #Appends both files
    cat dump_tmp.txt >> load_tmp.txt

    #Loads all the new parameters
    command="$load_command load_tmp.txt $NAMESPACE"
    eval $command

    #Remove temporary files
    rm load_tmp.txt
    rm dump_tmp.txt
  fi
fi

I called this script file "rosparam_append" and it takes as arguments the new .yaml file to append and the namespace (if there's no namespace, the simple rosparam load command is executed)

Example:

rosparam_append [path/to/your].yaml /[your_namespace]

you can use this script in your launch file (from this answer):

<node name    = "rosparam_append_node" 
      pkg     = "your-package-name"
      type    = "rosparam_append"
      args    = "$(find your-package-name)/path/to/your.yaml /your/namespace"/>

remember to give executable permissions to the script with:

chmod 755 rosparam_append

hope it helps