If you are still using time out to "punish" a child for "bad behaviour" then please read further and try to open your mind and change your ways. This is a humiliating experience for children and rarely achieves the outcome the adult had in mind.
Think instead of using the inappropriate behaviour as a teaching opportunity to teach a child a new behaviour through discussion. Show the child what they should do when this problem arises. Maybe they should use words to tell another child they are playing with that toy, rather than grab it back. Teach the words to say. Adjust the level of language to the child's age and development.
Children need to know that they have your support to get through these situations and will help with the other child who also needs to be taught how to ask, or wait for a turn. You may have to explain to an older child that a younger child does not know he/she must wait for a turn and has to learn this. Teach how to compromise and give a younger child a few blocks of his own so he won't take yours.
Model staying calm and in control for children. Let them know you are there to listen, and help. This calms a child substantially to know you will be there.
Of course, you will still have screaming red faced crying children who flail themselves about and aggressively attack others. At this time, you will need more patience and will have to dig deeper to stay calm. Give the child some space to let it out. This is natural and anger has built to a point where it must come out. Stay quiet and do not upset the child further with insensitive comments. Let the child know he/she is still loved and hold the child when they come to you.
Find a way to solve the problem while the child is upset to distract yourself from anger. Please do not walk away or isolate a child in a room - there are many things wrong with this approach. Keep them close, in view, and touch them gently if they will allow it. The child is not intentionally trying to make you angry. It's all about their own emotion. Keep your emotions in check. When the child is ready, talk about feelings and name them, offer an alternative/compromise that is acceptable. You are still in charge of the situation, you are just recognizing that the child has something to learn. You are the child's teacher.
If you give in at this moment you must know that next time there will be a bigger tantrum. Think of this process not as a power struggle, but an opportunity to discuss and solve a problem that leaves you both feeling good. Chances are, the number of incidents will decrease when new skills to have needs/wants met are learned. It's a process that takes time.