Hey I can totally relate with your problem, see this can be solved by following 2 steps, first is try prolonging the starting sound with more duration, what I mean by this is that if you are not able to speak rooorkee using this, then try extending the prolong little more to speak like rooooorkee. Don’t restrict yourself in prolonging more, in starting it can feel little out of comfort zone but trust me, with time, this extent will be in your hands. Second step is to give it some time and also prolongate on some words which are easy for you . What this does is that it programs your mind to perform prolongation at tough situations. It sharps your prolongation skills. In initial stage it may seem a conscious effort but after some time, it will become sub conscious and you will have full control over it. Also add an enjoyment touch to it, it will become easy and natural for you to prolong.